It should be for everyone asserting patent infringement allegations, not just "trolls". That way, they would at least think twice about using trivial patents against others, knowing that if they lose the trial, they have to pay the winner's expenses.
It would also encourage some companies to take companies who are asking them to pay "patent fees" to Court if they think the patents are not good enough, and they could win.
I don't think definition of "trolls" is a sensible way to handle the problem either, but I think the idea is that if you don't restrict it to trolls, then Google can wantonly infringe on a patent owned by Joe Littleguy. Joe couldn't possibly risk suing Google when he might be responsible for the millions in legal defense that Google could rack up in a heartbeat.
It would also encourage some companies to take companies who are asking them to pay "patent fees" to Court if they think the patents are not good enough, and they could win.