Um. . . why do we need a Twitter for Mac app? It's a website. You can use a web browser to access it if you want to. Non-issue.
...If I may ask you Twitter folks, why is a native application really necessary for OS X?
For the same sort of reasons that many people use native email client apps like Mail, Sparrow, etc. - e.g. smaller screen footprint, added functionality, better GUI, etc. Some prefer in-browser, some native.
Rumor: Twitter buying TweetBot for MAC
Possible. Not sure how much they paid for Atebits in 2010 (developer of Tweetie, which became Twitter for Mac & iOS) but that sum would be a write-off if they now buy TapBots.
Don't forget, TweetDeck was bought by Twitter.
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Maybe TweetDeck will eventually become the Twitter App.
Again, possible. Maybe we'll see TweetDeck and TweetDeck Lite, or TweetDeck Pro ($$$) and TweetDeck Free.
Twitter integration into Mac OS. That's why.
This doesn't include an actual Twitter client - as some have said. OS integration will make it easier to post stuff to Twitter (photos, web links etc.) but doesn't do anything (yet) for viewing a timeline & interacting.
Unless of course Apple are toying with the idea of integrating Twitter support into the Messages App; Apple certainly have the financial clout to strike a better deal with Twitter over API tokens than, say TapBots.
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Oddly the official twitter iPad app is really nice and well thought out. Hmm.
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YMMV but IMHO I find the native iPad app the worst of the three. I don't like their implementation of the swipe functionality - just seems like trying to cope with three of four loose pieces of paper on a windy day. It was the iPad that converted me over to TweetBot. Shame I missed out on the OS X alpha but hopefully the real thing will be in the App Store soon. But, each to his/her own
Maybe because 99 percent of the World is on Windows
Ignoring the debate about percentage market share

- remember that Twitter for Mac is actually the former Tweetie app, which was always a Mac-only client (plus its iOS counterpart). So, if they bought it and were then disappointed at market share, they only have themselves to blame.
