I've done PIF chains. Here's the problems I encountered with them:

1) People love to get discs, but getting them to PIF themselves is an entirely different thing.
2) People request things, then get mad when others simply don't have them to PIF.
3) People request something you have, then get mad when they don't get it exactly the way they'd wanted it (for example, my PIF copies of SW:Revisited included a printed cover, but no disc label - I got complaints about the lack of a disc label and the fact that the cover was printed on standard inkjet paper. Then I ran out of cases to put the covers in, and being a poor college student wasn't able to get more, and got complaints about the discs being without labels in little CD envelopes.)*
4) Since you can't keep doing this forever, you count on others to PIF as well, but when you turn down more offers, no one else takes your place and people get mad at you again (kinda goes with #2).

*Note that there weren't as many complaints as that implies. Most people were nice about everything.