"...coding not for Windoze but for OSX ChromeOS and Linux."
So, which distro? Which patch level(s)? Which browser?
Some of it can be guessed at (esp. in OSX), but stop and think about this for a moment... popping a *nix box isn't as simple, nor is it as straightforward.
As for the marketshare claptrap, will someone kindly explain why MacOS 9,8,7, etc had a rather decent pile of viruses floating about for them, but OSX blackhats are forced to rely on trojans and extremely stupid users to get their wares installed?
( g'wan, say the same for Windows, but read this first: http://news.cnet.com/8301-27080_3-20006478-245.html )
As for this bit:
"the security risk to ANY OS is directly proportional to market share (ubiquity). "
If that were true, then 5-10% of all malware out right now should be OSX-related... instead the number is (roughly) 0.001% (give or take a decimal place).
Now - all that said... the truth lies somewhere in-between. Yes there are market-share factors, but anyone who claims it to be the end-all be-all is a fool. Likewise for anyone who claims that any OS is infallible.