The speed issue is less about ability than it is about value. If you're drafting a WR in the Top 5, he better have game-breaking speed. Anquan had a great individual year, that's true. But which games did Anquan's efforts help us win? His big receiving days were all in games that ended with Big Red in the "L" column.
On the other hand, Randy Moss's big days fundementally change the outcome of the game, because there's really nothing that you can do to stop him. Look at this season's games versus GB, SF, DEN, SEA, KC. When Randy's having a charactaristic great day, you have to design your defense totally to contain him. Remember: the Vikes were without their two other weapons, Bennett and Culpepper, for long stretches of the season.
Steve Smith's explosion late in the season opened up the entire offense for the Panthers in a way that not-so-fleet-footed Mushun Muhammed never did nor could.
I just think that if you're going to invest such a high pick in a player, and such an amount of money, that better be a player that has no physical weaknesses. Route-running can be taught, hands can be taught (technique-wise), play recognition can be taught. Speed and size cannot be taught.
In the later rounds, the comparitive risk of using a 2nd or 3rd round pick on a player that can catch the ball but can't get behind the safties is much lower.
Drafting Fitz makes sense for the Raiders, because they already have a wideout with game-breaking physical tools in Porter. They could then have a 1-2 WR matchup with both a big-play WR and a possession, YAC WR.
The Cards lack that big-play WR right now. I believe that Bryant Johnson can fill this role as he develops. I do not believe that it's a good idea to invest so much money on a bunch of very young players at one position where it's very hard to distribute the ball so that each player can be used to their potential. It makes more sense from a value point of view, considering what the Cards already possess, to spend the #3 overall on a safety (Shaun Taylor), who can impact every defensive play, than on another wide reciever.