According to British carrier O2, Apple will be issuing an update this weekend to fix an SMS exploit that could conceivably allow any jerk with enough know-how to bulk-hijack iPhones. It's an admirably quick fix to a comically terrible problem.
But at least Apple's got an update infrastructure to match their relatively quick remedy; what's really worrying is that some other vulnerable phones—mostly Android and Windows Mobile handsets—are still vulnerable, and whatever updates Google and Microsoft have in store may have a slightly harder time blanketing users without the near-daily update checking built into the iPhone's usage style. UAnd so we will all die, by text message.
UPDATE: Google has patched the exploit in Android, where it was never as dire a concern anyway—your phone could be knocked off the network, but not hijacked.
UPDATE 2: The patch is showing up in iTunes for some folks already. —Thanks, Graham!