From turnout guru Michael McDonald, who is in a position to know:
As someone who works in the quarantine room on election night at Edison Media Research, I can tell you that we will not make a call if a race has the potential to be in a recount situation. In a close race, we review the recount procedures and consider what we believe to be the outstanding absentee and provisional ballots before we are willing to make a call. It is not the job of the media to prejudge the election process when there is a possibility for recount procedures to take place. Think: Florida 2000.
If the Obama campaign makes a formal statement that they concede Missouri, then I would expect the media would call the election outcome. My guess is that they will wait until the results are certified to make a decision if they will request a recount. As we have seen in Minnesota, there can be human errors lurking in the results reported to date.
The big picture: the Obama campaign has every right to a recount if they want one, and the networks aren’t presuming to make that judgment for them. There is also a small but tangible chance of a material human error in the vote tabulation.