ANALYSIS:  First of all, if the draft goes as scripted so far, I expect the Niners to seriously attempt to trade down from this spot.  If forced to pick here, the Niners have serious need at safety, wide receiver, and, until the signing of Marvel Smith, at offensive tackle.  Even with Smith, Andre Smith is a tempting prospect as a road-grader right tackle for Frank Gore.  With no safeties or receivers valued this high, the team must decide between Smith and a defensive end.  Aaron Maybin and Everette Brown are both talented pass rush specialists, but I expect that Mike Singletary will want a 3-4 end that is big enough to hold at the point of attack.  Robert Ayers is 20 lbs heavier than either Maybin or Brown.  Singletary wants a physical ("with an 'f'") team and Ayers seems a more logical pick.