I've been trying to ditch him all offseason in Dynasty leagues. I just acquired Davone Bess and a 2nd rounder for him and am quite happy about it. You just can't trust the dude.
I personally think you panicked. I would have rather held and got, at worst, a late 1st for this guy after he had three straight hot weeks, or even a player through 6 weeks who might be quiet (see Randle). Davone Bess is a drop and Sid is certainly worth more than a 2nd rounder.
The other side of that possibility, however, is that he gets banged up in the first month and then, after yet another injury, you can't cut him and you can't trade him. I think people that own Sid realize much more of the detail than people that don't. People that don't own him will generally say "yeah, he's hurt a lot". People that own him know all about the concussions and the general lack of him staying on the field for more than a month at a time. I don't like to be one of those people that say "if you take this away, then this" but after 5 years in the league, sometimes when you takes something away, its because that something is the outlier and not just the stat that makes your point look better. In Sid's case, its starting to look like the outlier.
He has played in 15 games in the last two years so he's a half-time guy. If you take away that one year in 2009, he has never posted 500 yards or more than 4 TDs in a season. Most of that is these nagging things that keep himd down/out.
Like others said, its never the talent, but when you look at it as a whole, 80% of his career has shown him to be a bottom-line "not very good" player (tossing all the details aside on health and playing and just looking at the bottom line..the points he gets an owner on a given year).
I agree that he COULD be worth much more but I'm inclined to sell him if I were an owner. Just don't trust the long-term.