I don't think it's regional. I'm in Sweden and if I visit the Flash install page with IE I get Chrome as pre-selected and if I visit with Firefox I get the McAfee add-on. (And when I'm using Linux, as usual, there are no extra applications installed.)

That's a good catch. The browser thing seems logical. I tried all the permutations I could:

Chrome - McAfee

IE9 - Chrome & Google Toolbar

Firefox - McAfee

Probably the stub found that you already have Chrome installed.

A webpage finding out what software I have installed is all kinds of bad, esp if there is no flash involved since its the page to download flash.

Well, it can certainly find out what browser you're using.

I'm in the UK and it did this - fresh install of Windows 7 (in a VM)

It's the same in Lebanon.