About three weeks ago, Facebook and Twitter ended several weeks of serious talks, in which Facebook was offering to acquire Twitter for $500 million of its stock.

While rumors of Facebook’s interest were brought up in an interview with Facebook CEO Mark Zuckerberg at the Web 2.0 Summit a few weeks ago, some shot down the idea as silly.

Quite incorrectly, as it turns out, since top execs at both Facebook and Twitter were right then at the tail end of discussions, which were initiated by the privately-held Facebook in mid-October, about bringing the two together.

Those talks, sources on both sides said, are now over.