Here's the scoop from NFL.com's Prospect Profiles:
"Blackmon made the switch from cornerback to wide receiver in 2005, and he is best suited to play receiver in the NFL. He has the size and strength you like in a receiver and plays surprisingly stronger than even his good size says he should. He is a very quick-footed receiver who accelerates to full speed very fast and has the shake/make-you-miss ability that makes him a very dangerous runner in the open field. He no doubt has to work on some of the fundamentals of playing receiver like routes and get-off, but he already does a good job defeating the jam and keeping the defender on his back when he runs quick hitting routes. An added bonus is that he is a very dangerous return man who will be able to make an impact returning punts and kickoffs early in his career. He is going to need some time to develop his skills to become the receiver he is capable of, and it is going to take at least a season as a backup to develop and learn the postion. In time, he will become a good starting receiver who is a dangerous big-play threat every time he touches the ball."