The tweetdeck entry should note that twitter, in acquiring it, threw away their entire product and rewrote it from scratch with less than half the functionality; thus making it less an acquiry and more of a snuffing.
That's still an acquisition. Companies get acquired for a variety of reasons and not all of them are because the parent company wants it to succeed/improve.
The only reason Twitter bought Tweetdeck was that Bill Gross was threatening to make a "twitter rival", and acquiring Tweetdeck would have given him a massive springboard audience and Twitter graph data.
Twitter acquired Tweetdeck to throw it into the toilet, basically, so that someone else couldn't benefit from it. Nothing wrong with that.
