Twitter may buy Virginia-based Summize, a Twitter search engine, says Jason Calacanis. A source close to Twitter says that the two companies have been in discussions around a merger over the last couple of weeks, but won’t comment on whether an actual sale has occurred, or the terms.

The deal certainly makes sense. Unlike rival Friendfeed, Twitter still lacks a search feature. And Twitter has relied on Summize in the recent past to help reduce load on the Twitter API. Summize is also one of (or the only) Twitter partner that has access to their XMPP stream.

Summize employees have recently been spotted at Twitter HQ as well, although that could be explained by the close working relationship.

Summize has raised just $750,000 in an angel round of financing. Twitter has raised over $20 million.