FWIW I used the word "pipe" very loosely to mean everything to the left of the interpreter. That means the unix pipe itself, but also the curl program, OS feeding it, network it's on, remote server feeding it, etc.

There are several scenarios where that logical pipe can fail. It doesn't have to happen cleanly on a 64-kb unix pipe buffer boundary. Some examples may include someone bouncing an office router and all TCP connection states getting reset, a neighbor microwaving lunch and WiFi radios croaking, a carrier having networking issues and connections timing out, the remote server restarting the web server after a software upgrade, etc..

I'm not sure curl (even with -s) will gracefully handle all of these cases defensively (doubly-so if the HTTP server was sending back chunked-encoding without explicitly specifying a Content-Length)

(anecdotally, since you mentioned flipping bits, it's possible but unlikely until you have to deal with it - http://mina.naguib.ca/blog/2012/10/22/the-little-ssh-that-so... )

At the end of the day, having not even considered what an active attacker could do but just what could naturally blow-up a small percentage of the time I'm inclined to say "that's bad, mmkay?" and try to persuade developers not to push that as a safe installation method. Even if they've triple-checked that the code they've written + interpreter can not possibly do harm in that case, the signal we should be sending (primarily to end-users) is that this may be an unsafe operation.