IMO there are two problems when drafting WRs:
1. Over-hyped - I think the WR position is over-hyped to begin with. They are by nature big-play guys and the media tends to glamorize the big catch more than any other play. This makes it appear that a big-play WR is the most important player on the team when in fact he is one of the least important players (outside of kickers & punters). That's part of the reason why I hate guys like Terrell Owens so much, they think the team can't win without them when in reality they were a relatively small part of the team's success. Nearly every other full-time position is more important to a team's success than WR.
Obviously, a good WR can help his team and a great one can make those big plays that you need at times, but your WRs just don't touch the ball often enough to make or break a team.
2. Team they are drafted by - Typically, the team selecting in the top half of the draft sucks and usually they don't have a very good QB or defense. Taking a WR that early in the hopes of fixing their problems is a trap that sets them up for continued failure as a WR, no matter how good he is, cannot even get the ball unless they have an O-Line that can give their QB time to throw and a QB with the accuracy to get the ball where it needs to go. Teams draft early in the 1st round tend to lack those two vital ingredients. A team that loses more games than it wins needs something other than WR.
As Fuzzy said, the WRs that had some success usually went to a team with a good QB. Teams with good QBs usually aren't drafting high so the WRs taken later in the round seemed to have better careers.
