If Google were to buy Twitter, they wouldn't do it because they want Twitter's content or community, they'd do it to merge Twitter's single-digit display ad share with theirs and defensively eliminate a future competitor. I feel they have no more interest in Twitter than does Facebook.

Twitter acquired Crashlytics, and they released Fabric.io as a "Twitter Inside" SDK to entice app developers to Twitter integration and its MoPub ad network. This is their big push to beat out Facebook and live inside every app, but Google already plays this game, and Twitter isn't yet a huge threat to them. Either Google or Facebook could buy them defensively, but they need not at this time. (I feel that Microsoft's purchase of LinkedIn was also defensive, but that's a different story.)

Verizon, on the other hand, could buy Twitter. They bought AOL to enter the content creation market, and they could cement their share. Or more likely, they could instead buy Yahoo, and with it Tumblr, on the cheap.

Amazon could buy Twitter. They bought Twitch, and they could use Twitter to expand their social presence, logged-in time, and display ad share.

Yandex could buy Twitter. They would break into the US and Japanese market in a huge way. The Fabric.io SDK would be a perfect fit to drive more engagement from apps to their properties.