They put a cap on how many players you can interview and work out something like 28 I think. More often than not the players they interview and or bring in are guys they have the most question marks about or the most curious about. Most of the time its leaked who they are talking either through the player or the team leaks it themselves.
There is so much hysteria about the draft every year. In 07 I dont remember them bringing in JaMarcus, Megatron or AP and Al Davis during the press conferance announcing Lane Kiffin, stated that all 3 where spectacular. They did bring in Zach Miller but thats because they knew who they wanted in the first round, they also brought in Brady Quinn who they felt they could either get cheaper OR later in the draft if they went elsewhere than Russell.
Every one of those players mentioned above are likely to fall out of the top 5 and maybe even top ten, some may even go undrafted or drop very fall in the draft. Its just covering the bases.