[dedward]

The only way they can fight back is to invalidate the patent or prove it doesn't apply to their situation.

And "patent trolls" tend to collect and file tons of almost meaninglessly broad patents and hten send armies of analysts and lawyers to look at them and find some small or big fish to sue, depending.

In this case, the patents were filed by Mr. Allen's venture itself, a venture created as a think-tank to do research and come up with ideas - which were then published (via the patent mechanism) for the world to see, and potentially license - all they had to do was keep an eye on the patent system and contact the right people to ask for a license.