If an offense is geared to include the running back as a main receiver I think it's fine that the running back gets a lot of receptions. Look at Tomlinson with over 100 catches a few years ago or Faulk with over 1000 yards receiving. These are products of the systems set to utilize their players talents. Davis is a good receiver out of the backfield. Over the past 3 years he has averaged 400 yards receiving, but his receiving touches came more off of dumps and safety valves. It still counts the same in the stat column, but I'd rather them get him the ball on designed plays in the flow of the offense rather than dinks and dunks.
As for how many running backs have averaged 1000 yards the last 3 seasons:
Jamal Lewis, Shaun Alexander, Tiki Barber, Clinton Portis, Edgerrin James, LaDanian Tomlinson, Rudi Johnson, Warrick Dunn, Domanick Davis, Fred Taylor, Ricky Williams (with or without counting the hiatus year), and Curtis Martin. So, that's only 12 backs that have averaged 1000 over the last 3. A few others of note, though.
Corey Dillon averaged 970 over the last 3, but is well over 1000/ season as a pro.
Thomas Jones averaged 970 over the last 3
Larry Johnson averaged over 1000 over the last 2, but didn't play much in that 1st year.
Willis McGahee averaged over 1000 over the last 2, but didn't play in the 1st year.
Reuben Droughns averaged over 1000 over the last 2, but didn't play much before that.
There are newcomers that haven't played 3 years yet: Cadillac Williams, Steven Jackson, Willie Parker, Julius Jones, Kevin Jones, and Ronnie Brown.
If it weren't for the sharing of duties that a lot of teams are going towards you'd see 20 backs with over 1000 yards. That's why I said it wasn't "special" anymore to get 1000 yards.