After reading through the '761 patent, any operating system which initiates a user working-space at login, e.g., a shell, will fall under the main claim of this patent.
It's refreshing to see somebody at least try to read the patent. I have a hard time believing anybody could mis-interpret it this badly though. Let's look at part of claim 1:
a computer-implemented tracking component of the network-based system for tracking a change of the user from the first context to a second context of the network-based system
How would an operating system with a shell qualify as a "network-based system"? Answer: since it's not network-based, it's not even close. Even something like logging in remotely isn't really network-based -- it's based on one computer, and happens to have a network between the CPU and the terminal. Here they seem to be talking about something that's truly network-based -- something intended exclusively (or at least primarily) for access over a network, and (quite possibly) the "server" isn't necessarily a single server, but itself an entire network. Exactly what "network-based" means for this patent doesn't seem entirely clear to me though -- and the patent specification doesn't really tell us either (the phrase "network-based" isn't mentioned in the specification). If that claim is part of the lawsuit, there will probably need to be a "Markman" hearing to decide how the claim should be construed. The court is required to presume that the patent is valid, and therefore attempt to construe the claims in a way that doesn't make prior art obvious -- and in this case, I think "network-based" is pretty easy to construe as meaning something that prevents a normal (or even remote) login from being prior art, so if the issue arises, there seems to be little question that the court would do so.
For those who've talked about tagging being an infringement, I'd note that "metadata tagging" is specifically mentioned in the "background of the invention" as being known related art. Likewise, those who've talked about a: "one to many relationship" (or various similar phrases), that's also mentioned in the background of the invention as already being known, not falling within the patent.
Now, I'm not going to try to argue that the patent is necessarily valid -- that's a question the court will probably need to address, and if Facebook's attorneys are doing their jobs, they'll (have specialists at prior art searching) put a fair amount of effort into researching reasonable possibilities of prior art. It does look, however, like if there is prior art, they probably really are going to have to do some serious work to find it. It might well exist -- quite a few people have been working on similar ideas around the same time, and it's entirely possible somebody else beat these guys to it. If it is out there, however, it's going to take quite a bit of hard, careful work to find it and show that it really does include all the limitations in the claims of the patent.
Just FWIW, I'd also note that to invalidate a patent, you don't just have to find prior art to one of the claims -- you have to find prior art for all the claims, or at least all the claims at suit. Looking at their dependent claims, we find things like:
30. The system of claim 23, wherein the first user workspace is associated with a plurality of different applications, the plurality of different applications comprising telephony, unified messaging, decision support, document management, portals, chat, collaboration, search, vote, relationship management, calendar, personal information management, profiling, directory management, executive information systems, dashboards, cockpits, tasking, meeting and, web and video conferencing.
I don't think Facebook provides all those, so they're probably not being sued over that claim, but for statuatory prior art to invalidate that claim, you'll need to find a web site (or something similar to a web site anyway) that provided every one of those applications by December of 2002 (and, of course, did the automated metadata-updating based on context, etc., cited in the earlier claims). It's certainly possible such a thing existed -- but if so, I'm pretty sure it's going to take some real work to find and prove it.