Dirac is good for storing video, but not efficient for streaming and real time communication, so it's not an option. Theora is inferior to H.264 in quality and VP8 really is the only open alternative as of now. So lock in or not lock in - what other open options are there? None. If Daala would emerge - there will be more. Also, hardware accelerated decoding always lags behind in adoption. Even for VP8 it's not widespread yet. So for any other newcomer it will be even more scarce.

About codecs - it's not just the license of the encoder/decoder or availability of open source versions (H.264 has open source encoders/decoders). It's about royalty free usage with that.