DeAnthony Thomas was too small to play RB too, which is why USC and most other schools recruited him as a CB. Oregon realized that some guys are just too good with the ball in their hands to not take advantage of that. If Elder is electric with the ball in his hands, you get the ball in his hands.
Elder's not going to be a prototypical RB, nor was he recruited to be that. If Coley is a good OC, he will utilize Corn in a similar fashion as Oregon uses Thomas. Line him up in the slot, at RB, out wide and get him touches on handoffs, end arounds/sweeps, screens, quick passes and deep routes.
The chances of him being a CB are going to be extremely low if his high school playmaking ability translates to the college level in a similar manner, say, 70% as good as Thomas' transition. Although Thomas is faster than Elder, they are very similar players in size, stature, and playing style.
[video=youtube;XAs9awnLlrg]http://www.youtube.com/watch?v=XAs9awnLlrg[/video]
[video=youtube;5hq1BrWdEeg]http://www.youtube.com/watch?v=5hq1BrWdEeg[/video]