Richard Stallman discusses the possibility that GPL version 3, as yet to be released, will force web companies that base their services on GPL software to release the source code:
The article can be read at ZDNet
How bad this will be will depend on the "linking" clauses. If, for web application software, the GPL only applies to code "linked" to GPL code, then this makes sense.
However, if they modify the GPL such that the "linking" clause meaning is extended to mean "use in a more general sense" then this could kill Linux pretty much over night.
Consider the two scenarios. The first is you use some GPL libraries or code directly in your own web service like a GPL'd htmleditor control. In GPL 2 you do not have to release your code since you are not distributing it. In GPL 3 you would have to release the code because it "uses" GPL code.
However, in the second scenario, if the meaning of "use" (or "link") is extended, then you might be forced to release any code you run under Linux as a service because Linux is licensed under the GPL.
I doubt the second scenario would come to pass. It would make free software virtually impossible to adopt for anyone except hobbyists.