I couldn't disagree more. Blackmon, although a guy with what appears to be a serious issue, is a young, elite level talent. I'd much rather gamble on that than a small passing down backup RB who will likely have a short shelf-life in fantasy. Regardless of the makeup of my roster.
Why are we to assume that he has a short shelf-life? The guy I most compare him to - Darren Sporles - looks very fresh at 30 YO.
Woodhead is putting up RB1 numbers in PPR formats - "small passing down backup" or not. The value that provides is significant, and could certainly be the difference between playoffs and missing - potentially more than that.
Blackmon is a WR3 now, in my opinion. If I am competing, I'd move on from that for a few years of boderline RB1 production.