Google+ may or may not be a viable contender in the social networking space, but Google sure is committed to it.

How committed? According to venture capitalist Fred Wilson of Union Square Ventures, which owns a stake in Twitter, Google’s passed up the opportunity to buy the popular microblogging social network several years ago.

“Google hasn’t been interested in buying Twitter since they committed themselves to Google+” Wilson told former TechCrunch chief-turned-venture capitalist Michael Arrington at TechCrunch’s Disrupt conference in New York City.

According to Business Insider’s account of Wilson and Arrington’s on-stage dialogue, Twitter CEO Dick Costolo made an overture to Google several years ago and indicated that Twitter could become a Google property for a sum in the $5bn range, but that Google was so focused on Google+ that it didn’t bite.

If the story is accurate, will Google’s failure to snap up Twitter “be a mistake that haunts Mountain View for years to come” as TechCrunch’s Josh Constine suggests it could? Or was the search wise to save its cash and invest in a homegrown effort that may or may not go anywhere?

It’s easy to look at other buyouts that didn’t happen, like Yahoo’s missed opportunity to purchase Facebook for $1bn in 2006, and suggest that Google should have purchased Twitter. After all, Twitter has since raised bundles of cash at a significant ten-figure valuation that all but eliminates the possibility of an acquisition.

But a $5bn Twitter deal would have been a risky bet for Google for obvious reasons.

Twitter appears to have a real problem with user attrition, its monetization efforts are still a work in progress and, like Facebook, it faces significant challenges related to skyrocketing mobile usage. If Twitter can grow its userbase, develop an ad model that works and find a way to capitalize on mobile in a big way, it’s always possible that Twitter at $5bn could be looked back upon as a bargain. But that’s a big if.

Google’s acquisition track record is, of course, subject to debate. Which is sort of to be expected given the number and diversity of the deals it has completed. But one thing is for sure: having made a number of nine and ten-figure acquisitions over the years, it’s not gun shy. So the fact that it didn’t jump at the chance to snap Twitter up for billions may say more about Twitter than it does about Google.