If I have 100 sites on a wordpress multisite installation and I give admin access to multiple developers, how can I protect the system from choking if one of them writes an infinite for loop?
This is technically a server configuration question and therefore a candidate for ServerFault.com
You should be insulated against infinite loops by setting a smart upper limit on PHP's max_execution_time (30 seconds by default), preventing users from accessing PHP's CLI, and otherwise keeping on top of server administration.
My suggestion would be don't give them access to the production server, just to a dev/staging version.