Big is ugly (in a corporate sense)
The collapse of the Pru's attempt to buy AIA of Asia for more than £24bn is an important event in the history of British stock-market capitalism.
It shows that conventional investment institutions are prepared to act more like the independent owners of a business and not as absentee landlords too readily compliant with the wishes of managers - which is how their critics would characterise them.
In this rare case, it was the Pru's own shareholders who frustrated the takeover - by making it clear that they thought the purchase price was too steep and by telling the Pru's directors that they would vote down the deal.
The implications are significant.
The Pru's chief executive and chairman may have to resign, having wasted hundreds of millions of pounds of shareholders' money on a deal that won't happen.
But perhaps more importantly, it shows that investors have become much less supportive than they were of companies that want to become global giants through takeovers - since gigantism has often led to monstrous blunders.
After the woes of those enormous banks - from Citigroup to Royal Bank of Scotland - and the current humiliation of bid-bloated BP, it's not surprising that shareholders now see big not as beautiful but as grotesquely, dangerously ugly.
What investors have learned is that there are limits to the benefits of geographic and product diversification.
When a company becomes bigger and less reliant on a limited number of products, services or customers, there is reduction in the risk of serious setbacks up to the point where human ingenuity and information technology can actually monitor the risks being run by said company.
What we've learned in the last three years is that a number of massive global businesses - especially but not exclusively in the banking sector - grew well beyond the limits were any mortal could have a proper grasp of what was going on in the myriad nooks and crannies of those businesses.
Which is why, as the Pru's management have learned the hard way, investors have become much more wary of companies that want to carry out mega, "transformational" takeovers.