Here's the qualifying protocol for the WCs this year (IIRC):
In each event, if you have the reigning champion, s/he automatically gets to go.
In addition, you may send up to three additional athletes. You get one person with the B standard, plus up to two A standard runners. Countries may choose these runners however they please.
HOWEVER, USATF has further stipulations:
1) The defending champion gets a "bye," but s/he MUST at least compete in one event (to prove they s/he isn't injured, I guess). That's why Lagat was screwing around in the 800m.
2) ONLY the top four finishers in the event's final are eligible for the three A/B spots. So, neither Alan Webb nor Will Leer could make the team, even if NOBODY in the top 4 had a time standard.