I would have gone for 1000 to 1100 yards no matter what, but you should have included options for fewer than 1000 yards.
Remember that Maroney had just 745 yards in 2006.
We MAY go with Maroney as our dominant back this year, but he could get injured or we could go with a tandem again. (Morris could do more than I expect from him, and we could pick somebody up in the draft.)
Even if he is our dominant back, I think we'll see a much heavier focus on the pass this year.
All things considered, I think there is a ~40% chance that Maroney does not break 1000 yards rushing.
None of these comments should be considered to be a knock on Maroney. At the beginning of last year I loved his moves to the outside, but I was very concerned about his ability to run inside. As the season progressed (but before he got injured) he showed us that he could both run inside and catch, so I am very excited about his 2007.
I just don't see us giving him 300 attempts. (Nor do I think its advisable to do so. Running backs can break when you use them too much).