Obviously, if you stick a lot of files in one folder, the efficiency of various file operations is going to go down (e.g.
ls takes a lot longer). However, what's the limit for how many files you can stick in a folder before it chokes on you? Obviously, this may vary from file system to file system, but I would think that they'd at least be similar in their limits. Can you stuff files in there until you run out of disk space, or are going to run into some sort of limit like you can only put 65536 (or some other multiple of 2) files in a folder before your file system chokes on you?
I'm most interested in jfs, since that's what I use primarily use for my large partitions, but it would be good to know for *nix file systems in general.