Well it speaks to the 'trollness' of patent trolling. In the Prenda Law case (and other copyright cases) the judiciary has decided in many cases that the 'threaten with action' strategy used is an issue. Had this been a "real" patent case the patent holder would approach Rackspace, say we think you infringe on patent X and you need to license that from us or stop infringing. Then license negotiations begin, and then either they license it or they break of negotiations and it becomes a lawsuit.
The steps here of attempting to intimidate them into a favorable position without any way of knowing if they are in fact liable, is what pushes it into the extortion space for me.
No, the course of action I would try to take in this situation is that as soon as I was presented with this demand I would respond, "Either sue us and open up to discovery, or go away, and if you go away and try to sue us later we'll use that as evidence that you didn't really believe we infringed in the first place."
I don't know if you have ever been in a bar fight but I can tell you from experience that once the trouble maker has asked you if you just called them a liar (or some other affront) there really isn't any negotiation that is going to work, their is going to be a fight whether you want it or not so your best bet is to just start planning to win it.
When presented with the "possible infringement" demand Rackspace was already in the fight. Appeasement doesn't work, it can push off the start of hostilities (and that can be strategic) but the safe bet is to assume they are coming after you. (which I have to believe RS knew because they did the whole mutual forbearance thing).