Generally speaking I like the idea of
patterns in SW for many reasons. Two of the biggest reasons are that they save development time and reduce errors (not repeating other peoples' mistakes). For these same reasons security patterns seem to me to be a good idea.
One small advantage to roll-your-own security software is the fact that you did it your way and it's probably not exactly like 95% of the other systems out there. If someone discovers an exploit through your security it pretty much just affects you. Or more importantly, if someone discovers an exploit for someone else's system it probably won't affect yours. However, if everyone is following the same sort of security patterns and an exploit is discovered for one of those patterns doesn't that mean that a lot of systems will be affected?
Of course, if a well known pattern is exploited it will probably be patched rather quickly where a roll-your-own system might never get patched (if the comprimise is even noticed).
_M_