Anderson and Fedor tapped to chokes, which are far less dangerous than head strikes (ask any doctor -- there's a reason several countries' medical associations want to ban boxing and MMA, but no country's association wants to ban judo or BJJ). If GSP is illegible, then they are even less eligible.
Least dangerous thing to tap to is chokes (no long term or short term damage if the ref stops it, which always happens).
Medium danger thing to tap to is arm and leg locks (small long term damage, major short term damage which can be repaired by modern surgery).
Most dangerous thing to tap to is head strikes (lifelong neurological damage which can't be repaired by any medical science).