The amount of time it has taken (and arguably will take) to stage the Opening Ceremonies has some British coaches feeling that the event will destroy any medal hopes for the host country. Since the Summer Games will take place in London next year, and the host country always goes last, British officials don't want to tire their athletes by having them stand around waiting for their turn.
As of now, a full boycott is still speculation. The entire British track-and-field field team, however, has officially boycotted the ceremonies, as well as triple-jumper Phillips Idowu.
Source: Yahoo! Sports