Or at least, portable apps shouldn't mix with patron PCs. In the comments, Rob lists the security risks that libraries open themselves up to when patron PCs are allowed to run programs from a USB drive: "keyloggers, spybots, and other hacks that let one patron send all the data from a patron station that doesn't get rebooted all day to an email or web page." Empowering patrons is good, but maybe not that much!
Based on my own test, LINK patron PCs don't allow portable apps to run. Check out the error message I got when I tried to run GIMP Portable on a catalog computer at Madison Public Library:
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