There is obviously a need to check that the bitcoin binary is indeed produced by building the source code which has (hopefully) been thoroughly checked. Otherwise someone could potentially introduce a backdoor to for instance steal bitcoins. This is especially important since I suppose most people using bitcoins do not bother with compiling it and as we gather more users, there will be more and more people using the precompiled binary.
To quote the README.md file:
The master branch is regularly built and tested (by who? need people willing to be quality assurance testers), and periodically pushed to the subversion repo to become the official, stable, released bitcoin.
In order to check the binary we need to be able to reproduce it exactly from the source. For that, we need to know the exact version of the compiler used, the exact version of the libraries used, a script that reproduces every step of the building process (modifications to the makefile, stripping debug symbols, ...), and anything else that I may have forgotten.
So please, whoever is in charge of creating the compiled packages (Gavin Anderson?), give us all the information needed to check them.