[Originally a comment on hacker news on 29th May]
H.264 / MPEG4 part 10 / AVC
it is patented which is a definite disadvantage compared with a
theoretical patent free codec but it has some real advantages.
1) The standard is controlled and defined by a collective industry group under the auspices of ISO. 
Most of the major players in video technology at the time took part in
the standardisation so are committed to FRAND patent licensing terms.
3) In almost all cases and commercial business models (that do
not involve Free software) the MPEG-LA H.264 patent license is really
very reasonable and unlikely to cause problems to an otherwise healthy
business. Note that the license Google has to the MPEG-LA pool of
patents while free is NOT compatible with Free software.
companies not in the MPEG-LA pool that popped up now with demands really
would trolls in the original sense that they have sat under the bridge
for a long time waiting for a juicy opportunity rather than being
upfront earlier. I don't think that this would help them in a legal
case although there is no guarantee that they don't exist. 
H.264 is really quite good although the latest codecs are showing what
can be done with further development and processing power.
H.264 decoding (and often encoding) is cooked into a massive amount of
existing and deployed devices in ways that cannot be adapted to VP8/VP9
by a software update.
For now H.264 is the no brainer option for
any commercial system although multi codec support may be worthwhile in
some cases. If you want patent free I recommend MPEG1 as I believe any
patents on it should now be expired or at least expiring very soon if
they were granted a long time after filing. I'm glad that Firefox has
backed down and will now use the OS codecs to allow playback of H.264.
The OOXML case shows that this isn't foolproof but in my view it is a
better option than the standard being controlled by a single company
even if the controlling company publishes the source code. This applied
to Microsoft when they offered VC-1 as a free alternative to H.264
(there is now an MPEG-LA pool) and to Google now with VP8 and VP9 now.
Google is the new Microsoft and has fully learnt the lessons of
"Embrace, extend and extinguish".
 Not Free software compatible
but better than nothing. And even Google's license to the VP8 patents
from the MPEG-LA pool does not seem to grant Free software compatible
 There is a greater risk of people popping up with
claims against VP8 or VP9 as they are newer and less prominent. The
MPEG-LA's call for a pool of patents has helped draw out those patent
owners and many have joined the pool and reached terms with Google
(although Nokia and maybe others haven't.
 Realistically for patent free greater than 20 years old is the answer so it probably needs to be MPEG1.