There's been plenty of rumor and speculation over the past few months that one of the tech titans -- Amazon, Apple, Google or Microsoft -- will buy Twitter before it gets any bigger. (Click on each link for the speculation). If any of that chatter is to be believed, Bezos, Jobs, Schmidt or Ballmer may want to step up sooner rather than later.

The latest comScore numbers reported by TechCrunch indicate that the short form communications phenomenon continues to attract users at a rapid clip. It posted 44.5 million worldwide visitors in June, up 19 percent over the previous month.

TechCrunch says that Twitter now is bigger than ESPN.com and slightly smaller in audience than the BBC and Craigslist. Not bad for a company that's got minimal revenue and only a few dozen employees.

At some point, it seems someone will want to tap that traffic base. But who will it be?

Of course, Amazon.com's Jeff Bezos -- an investor in Twitter -- has his hands full with the recent purchase of Zappos. Microsoft too has its own integration issues ahead with a recently announced 10-year advertising pact with Yahoo.

So that leaves Google -- whose CEO Eric Schmidt downplayed the possibility -- or Apple. Or, there's the possibility that another wild card could emerge. In fact, given the media's fascination with Twitter it wouldn't surprise me to see a buyer come out of those ranks.

Rupert Murdoch of News Corp. said earlier this year that he's not interested in buying Twitter. But others out there may want a piece of the fast-growing service.