I'd like to pull a paragraph from Arstechnica for this debate:
MPEG-LA's license terms for H.264 set out a range of fee schedules depending on the exact nature of the H.264 implementation. Importantly to web users, video that is distributed over the web and which is, importantly, not behind any kind of a paywall, is royalty-free. This means that uploading a video to a site such as YouTube and then rebroadcasting that video to all and sundry is free. For browser developers, the situation is not quite so happy: browsers include H.264 decoders, and these are subject to royalties. The size of the necessary payment depends on the number of units shippedâ€”browsers with fewer than 100,000 users would likely not need to pay a royalty at allâ€”but in any case is capped at $6.5 million (equivalent to about 65 million users), annually, until 2015.
, Arstechnica - Google's dropping H.264 from Chrome a step backward for openness
The MPEG-LA has since waived software license fees until 2015 in an attempt to gain adoption.
Given the current MPEG-LA Fee Schedule Firefox would have to start making royalty payments. I'm fairly sure that Mozilla wouldn't be able to afford that.
Perhaps a rogue patched version Firefox would become viable at that point but how much could one trust these patches? Would GNU/Linux distributions shipping H.264 patched versions of Firefox become subject to legal action?
An Opera opninion on H.264 as the <video> tag codec
We can either play chicken with the MPEG-LA and it's H.264 license fees and give VP8 more time to develop or we can hand web video over to a borderline patent troll now.
Remember, the first hit is free; they'll make their money back when you're addicted. ;)