I always think with receivers, there is a very very slim category of elite receivers who a defense just can't take away. Off the top of my head, this year that's been Megatron, Harvin, AJ Green. Pretty much every week WR1s. Marshall has been close but has had a couple of down weeks. Some you can depend on every week - not necessarily for a touchdown, but for a very good floor. This is the Welker/Decker category. Every week WR2s at least.
Then there's another category of guys who you have to be careful with, because essentially you're betting week to week on the coverage of the defense and the offensive game plan. You'd have to have Julio Jones, Mike Wallace, Hakeem Nicks, maybe even Victor Cruz in here - and of course Dez. In my opinion, taking risks on these guys and being able to manage them week to week separates an average fantasy owner from a great one. You need to know who shut down corners are, you need to know how teams manage their injury reports, and you need the guts to make a ballsy decision. If you can do this, you can get great value in drafts. Because you can draft Dez say 4 rounds later than Megatron, and perhaps you play him 12 times over 16 games, and you get 8 hits, and 4 dumps.
As a Dez owner, I've failed so far this year though to sit him at all, but now I do think I have the info I need to manage the situation. I've traded to give myself as many WR2 candidates as I can, and now in a very competitive 12 team league can start 3-4 (most likely 3) out of Dez, Stevie J, Denarius Moore, DHB and Mike Williams. I will not hesitate to bench him this week, for instance, if something flares up. And I'm going to try to buy myself some time to watch some Joe Haden film later in the week. I know AJ Green can torch him, but he's a different player from Dez. I will have no issues whatsover playing the two Raiders over him this week if I don't like the matchup.