Well, they are the only 'convicted patent troll' in the right definition of the term: http://www.idownloadblog.com/2013/09/06/apple-google-motorol...
Using SEPs for suing others is wrong. Google has learning marketing ploys from IBM, place ads in influential tech blogs, get lots of good PR, the same blogs will call anyone a patent troll but Google.
And because I know this will come up- Patents are not evil- the system is broken sure, people misuse trivial patents, but at the same time, people who put hard work in their work need to be rewarded (for meaningful patents). If I'm an academician and I've spent 5 years coming up in my life with something innovative that would otherwise have taken a lot of time, then I should have the option to sell it to someone who is better equipped to monetize it. It's like an author hiring a publisher. So patent consortiums are not trolls, they are like publishers. Google is because they misused SEPs.
Sidenote: I'm against those kiddish patents that are just about 'describing at technique in which x y z'. I feel the patent overhaul should involve the FTC creating a team that would decide the 'year' validity of a patent, and companies having to pay for it. That notwithstanding, Google is a troll. And just because it gives out free stuff, you guys like it.