Doesn't bother me, though I don't have any Birkenstocks. I probably have more online hours than most of the people on the board and have yet to get infected with anything running OSX. Doesn't really matter what the reason is and I don't care about market share. It is a non-issue at this point. I can't say the same thing about my son's laptop running windows. And given the number of threads on PPOT about windows viruses and malware, it appears to be significant with MS operating systems.
If someone asks about a solution for not having to deal with viruses and malware, to-date "running a Mac" is still a viable answer. It just may not be the best answer or the one that they want to hear