Well, I've found a possible reason to disable them by default.
The Debian Lenny/Ubuntu Jaunty libtool 2.2 appears broken with its handling of the libtool convenience library. Giving build failures unless they are configured to off.
Since I made the change to testbed "distcheck" I've been fighting with them. Something inside distcheck seems to be running configure with the defaults regardless of what the master test is run with. Probably the dist "configure --silent" packaging or a sub-test of the package it makes.
If anyone is able to help I'd be very grateful. If we can't find a solution to that one I think we are going to have to disable loadable modules unless adaptation needs them.
Amos -- Please be using Current Stable Squid 2.7.STABLE6 or 3.0.STABLE16 Current Beta Squid 3.1.0.9
