Shares in Zynga, the social gaming company behind Farmville, have fallen as much as 40% in after-hours trading following disappointing results.
It reported a net loss of $108m (£70m) for the first six months of the year, compared with a profit of $18m for the first half of 2011.
It slashed its forecast for full year earnings to between 4 and 9 cents a share from 23 to 29 cents.
It took the shares close to $3, well below December's $10 flotation price.
Shares in Facebook also fell following the announcements from Zynga. Its games account for about 15% of Facebook's revenues.
Facebook releases its own quarterly results on Thursday.
Zynga blamed its lowered outlook on delays in launching new games, a faster-than-expected decline in existing games and "reduced expectations for Draw Something".
Zynga bought Draw Something for $200m earlier in the year.