[fny]

I agree. Or how about one step away from just the installation? Once you load a gem it can do whatever the hell it wants to your system. This vulnerability feels very security-theater-ish. At the end of the day, someone needs to audit the gem or have deep trust in the supplying party (i.e. Rails) to protect against arbitrary file manipulation.

[Xylakant]

Installation and running are not necessarily done with the same account. Often, apps run with lower privileges than they're installed with, so the damage may be somewhat mitigated. I'd really treat that as a separate, albeit related problem.