Buried at the end of the Big 12's official announcement welcoming TCU to the conference was an interesting nugget:
The action of the Board was without dissent. On the advice of legal counsel, The University of Missouri did not participate in the vote.
While it's unclear exactly why Missouri's legal team did not want them participating, it certainly appears that the school is doing everything in its power to avoid the types of legal entanglements that held up Texas A&M's move to the SEC.
Missouri's Board of Directors voted to give their chancellor the authority to explore realignment earlier in the week, a clear indication of the school's interest in the SEC. The Tigers seem like a logical fit to get the SEC to 14 teams, but they were reportedly still a few votes short this morning.
The SEC has been leery of involving itself in any lawsuits that might result from poaching members of another BCS conference, so Missouri's decision not to vote on TCU may be an effort to reassure them.