Why would Google buy Sun? Google doesn't make hardware and Sun gave Java away for free. Google still gets to poach the best of Sun's programmers so what's in it for them?
Note that the alleged value of Sun's patents is based on essentially suing everyone supposedly using the technology and so the money put into such an investment essentially forces the buyer to either write-off the investment or go out and do the suing.
It may be that Google has decided it needs a business model based on the end of (or diminution of) software patents - ie, they could not buy enough patents to not have other entity siphoning off their revenue on a per-byte basis (see the WebM fight that's brewing).
Here's where the analysis of Oracle-shill Florian Mueller is especially insidious (http://fosspatents.blogspot.com/2011/01/google-is-patently-t...). Any "patently strong" corporation, any coroporation that builds-up a large "war chest" of their own "profitable" patents has a strong incentive to keep the whole patent racket going (otherwise, the lose the value of that "war chest").
Again, kudos to Google for not taking that route (and, they're doing this to make money, which is great too...).