No surprise there; Opera's market share is small enough that FB can simply code to the standard and worry about explicitly supporting the major browsers.

Although interestingly, if Opera accounts for ~2% of FB users (big if), then FB would have 16MM Opera users. Using the average of $4/user/year, that means Opera generates $64MM for them. That would be more than enough to justify throwing a few devs at.

Edit: Also curious is the pointless URL that page has. I would have thought FB would be using basic SEO on their help pages, so that someone googling "facebook supported browsers" would have a better chance at ranking first (it does for me, anyway). As an aside, the sub's page is actually the second result.

It's interesting because Opera is one of the links on the "unsupported browser" page.

I would actually posit that they make much less money per user from Opera than IE. Ie the type of individual who would click FB ads (or spend money on virtual gardens) is more likely to use the Windows default browser.