According to reports, Twitter has acquired third-party Twitter client TweetDeck. TechCrunch founder Michael Arrington says he’s heard from a source with “knowledge of the deal,” and that it will be officially announced in the next few days. He puts the price in the $40 – 50 million range.

TweetDeck has long been one of the most popular third-party Twitter clients, if not THE most popular. It’s probably safe to say that the recent return of co-founder Jack Dorsey to Twitter had a lot to do with the deal.

Dorsey was quoted as saying, in a talk at Columbia University, fresh after rejoining the company, “TweetDeck is a very interesting client, because it presents a view that no other client in the world presents, which is this multicolumn, massive amounts of information in one pane. And people really, really enjoy that. But I think that’s maybe five percent of the Twitter population. That five percent of the Twitter population are some of the most high-value publishers that we have, and they’re using the service at extreme velocity. So of course we have to pay attention to that, and I’m not saying we need to rid ourselves of interfaces like that. We have to embrace them.”

Well, they certainly do seem to be embracing it, and that 5% of the Twitter population should get quite an uptick if TweetDeck’s features get rolled into Twitter’s own interface.

“But, we also need to speak to the 80 percent that will not be using an interface like that, that don’t really understand what Twitter is and that see Twitter mainly as a consumption experience,” Dorsey added.

It would appear that Twitter has spoken.

We have to wonder what this will mean for other third-party clients like Seesmic, Hootsuite, etc. If they have already been competing with Twitter’s own user interface (which just got a makeover last year) and TweetDeck itself, this should make things increasingly difficult, and emphasize the need for more features to set third-party apps apart from the pack.

Just last week, TweetDeck launched a new version of its iPhone app.