The job description alone -- run real fast, get hit -- explains why wide receivers get injured at the rate they do. Scary hits, like the ones that left DeSean Jackson and Austin Collie lying on the field, are the ones that stick with us, but it's really the wear and tear that does it more than the big hits. We don't think about the jolts they take blocking or jumping and landing hard. As the body types of WRs have become varied, we're confronted with an issue of categorization. Not all WRs are doing the same job. We have speed receivers, possession receivers, hybrid receivers, big receivers and quick receivers. One size does certainly not fit all, so while the position is named with the one broad descriptor, it's much more important to think about the individual and his context than it is the "WR" slot on your lineup card.
Risk goes right along with this. Most NFL teams pair WRs up in ways that they feel will complement each other, giving the QB and the offensive coordinator options. It seldom works like this; speed receivers have to go across the middle sometimes, with the occasional innovation like the bubble screen creating new roles for those existing players to fit in. Once you've judged the risk for one player, you have to judge the risk of the player behind him, and behind him. A risky WR has to be backstopped with not one, but two WRs. That means there's actually hidden value in steady but unexciting receivers, though there's a risk of taking a WR2 behind a risky WR1 as well. A quick look through game logs show that the best example of this is Kevin Walter behind Andre Johnson. Walter just doesn't get the bump you'd expect when the WR1 is out. This pattern holds across the league more than you'd think, which makes WR handcuffing less necessary than most think.
With 64 WRs to talk about, some are healthy and will get nothing more than the "Healthy" designation. That doesn't mean he's without risk. It just means that you can pick that player based on talent and opportunity rather than making a huge risk adjustment. Get these kind of decisions right on draft day and everything else falls into place.