Chrome sandboxing doesn't rely on things like address space randomization and NX, so the Mac vs. Win32 different --- while probably still present --- may be less pronounced.
Opera Mobile has significantly more installs than Mobile Safari, but Safari probably has greater market share in terms of mobile visits (because iPhone users use Safari quite a bit).
As for numbers, Opera says there are more than 120m installations of Opera Mobile:
They have another product, for less powerful phones (it does rendering via a proxy actually) that has 20 million users. Since the requests are all proxies, Opera knows how many people use this product:
Since the rules change (i.e. become easier) each day, the day number gives you some indication of the relative difficulty in performing the exploit, even though the exploits themselves are prepared in advance:
"Windows, on the other hand, he claims is tougher because of its address randomization feature and other security measures. As for Chrome, he says that he has identified a security bug in Google's browser but has been unable to exploit it because the browser's sandboxing feature and the operating system's security"
Sounds like Chrome was saved by not having a version for the extremely vulnerable Mac. Security by obscurity is no security at all.
