Hamilton's tough decision
Since BBC Sport chief analyst Eddie Jordan reported on this website last week that Lewis Hamilton was on the verge of switching to Mercedes from McLaren next year, Formula 1 has been awash with speculation about the 2008 world champion's future.
McLaren did their best at last weekend's Italian Grand Prix to dismiss the story - team boss Martin Whitmarsh even joked: "Any sentence that begins, 'Eddie Jordan understands' is immediately questionable, isn't it?"
But it was noticeable that not only did McLaren not deny the story was true, they said very little to suggest Hamilton was staying with them.
From Whitmarsh, it was: "Lewis and his management have made their position clear to us", "my understanding is we're talking to him" and "I'm pretty convinced we will have a very good, competitive driving line-up next year."
None of which translates as "Hamilton is staying".
Hamilton was triumphant at Monza, but how many more races will he win with McLaren? Photo: Getty
As for the doubts cast on the veracity of the story, the source is strong and credible, and the core information - that Hamilton has agreed terms on a contract with Mercedes for next year - is based in fact.
That does not necessarily mean Hamilton will move but it does mean he is thinking about it seriously. And you can make what you will of his downbeat behaviour throughout the Monza weekend - even after he won the race.
In the paddock, the general view was that a move would be a mistake - but it is a much more complicated decision than that.
Firstly, McLaren have undoubtedly been more competitive than Mercedes in the last three years. Between them, Hamilton and team-mate Jenson Button have won 16 races since the start of 2010; Mercedes only one, with Nico Rosberg in China this season.
Over an extended period, McLaren have a winning pedigree beyond that of any other team. Only Ferrari have won more grands prix, and they have been in F1 for 16 years longer.
Hamilton, who has been nurtured by the team since he was 13, says: "I want to win." On pure performance, there's only one choice, right?
In F1, things are rarely that simple.
Yes, McLaren usually have a good car, but until this year it had been a long time since they had unquestionably the best.
It was close with Ferrari in 2007-8, although hindsight would suggest now that the McLaren was probably not quite as good then. In which case, you probably have to go back to 2005 to find the last time McLaren had conclusively the fastest car in F1.
This is known to have irked Hamilton in 2010-11, and played some part in the cocktail of issues that led to his difficult season last year, when his frustration at the car's inability to compete for the title and problems with his family and his girlfriend led to what he admitted was his worst season in the sport.
That all changed this season. The McLaren is again setting the pace. But a series of operational problems in the opening races badly affected Hamilton, costing him 40 points. Add those points to his current total and he would be leading Ferrari's Fernando Alonso, not trailing him by a win and a fourth place.
Hamilton has done well to disguise his disappointment publicly, but it was around this time that his management started approaching McLaren's rivals about job opportunities.
On top of that, McLaren are entering an uncertain period. For the first time next year, they will have to pay for their Mercedes engines - that's in the region of eight million euros they cannot spend on the performance of the car unless they find it from other sources.
Tied in with this is the question of salary. McLaren have made it clear they cannot afford Hamilton at any price. The word is they have offered him a cut in money for next season, on the basis that they cannot afford anything more. This might be offset by other compromises, such as over PR appearances, flights and so on.
Already on about half of what Alonso earns at Ferrari, one can imagine how that has gone down with Hamilton - especially as McLaren's portfolio of sponsors makes it very difficult for a driver to do personal deals elsewhere to top up his earnings. That's because almost anywhere he looks there's a clash with a company that has links with McLaren.
Meanwhile, Mercedes are by definition a "works" team with factory engines, have the might of an automotive giant behind them. They can pay Hamilton a lot more than his current salary - believed to be about £13m - if they want to. And at Mercedes there is also a lot more freedom for a driver to do personal sponsorship deals.
The funding for Mercedes' F1 team comes entirely from external sponsors - and the budget is reputedly significantly less than enjoyed by Red Bull and Ferrari. But it is underwritten by the parent company so even if there is a sponsorship shortfall it doesn't affect the team.
Performance-wise, the team that is now Mercedes actually won the world title more recently than McLaren, when they were Brawn in 2009. Ironically, the man who won it was Button. His success - and what he interpreted as the team's ambivalence about him staying - led to him moving to McLaren.
Admittedly, Brawn's success in 2009 was tainted by the row over double-diffusers that clouded that season. Once everyone had them, the car was no longer as competitive as it had been.
Mercedes have certainly been under-performing since then, but that can at least partly be explained by the fact that Brawn, facing serious financial problems, slashed their staff by 40% in 2009. As Mercedes, they have been slowly building levels up again.
The pressure on the team to up their game is massive - hence the huge investment in terms of staffing and resources in the last 18 months or so.
And while they are a long way behind McLaren this season, they are on an upward trend, even if it is significantly slower than either the team or the Mercedes board would like.
Equally, few in F1 would disagree that Hamilton is one of the three best drivers in the world, alongside Alonso and Sebastian Vettel. Mercedes don't have any of them.
It's impossible to know how much faster the car would go in their hands than it has done so far in those of Rosberg and Michael Schumacher. Some might argue not at all. But, that's not how Hamilton, who raced and beat Rosberg in their formative years, will look at it.
Add all that up, and the decision doesn't seem so easy after all.