@conanite:
I happen to work for RPX, and it's actually a very common misconception that people believe our model is identical to IV's.
The biggest difference is that RPX does not assert its patents, ever. It's our business model to protect operating companies making honest money from trolls. If you decide not to give RPX "protection money", we won't do anything to harm you. It's up to you to sign up for our services.
Another difference is that we also intervene in our clients' litigations, and help them resolve their lawsuits by buying patent licenses on their behalf. And we have advisory services for new companies not familiar with the rules of patent litigation, and patent market intelligence for those who want to keep up with what's happening.