Hmm. A bug by which I have yet to be bitten. Probably because I was lucky enough to get 'my' camera first time. I bought and OM2 back in the summer along with some lenses. And I'm loving it. Then I bought an Agfa Isolette and a Bronica ETRS. In addition I have a Canon EOS 20D.
It might be that I've avoided GAS because I landed on my feet with the Olympus kit first time, even to the point that it stopped me immediately buying an Olympus OMD. So getting the OM2 has probably saved me money at least in the short term, although I do want to migrate my digital kit to Micro 4/3 some time next year.
But the main impediment for me is the proliferation of lens kits. And at the moment that's keeping the bank manager happy because although I spend too much time looking at Feds, Zorkis, Nikons, Canons and heaven knows what (not to mention Leica bank breakers), the thought of yet another lens kit is stopping me actually going so far as to part with cash.