Yosh, one good example of what you are talking about is with Jeremy Mack. He was injured his junior year and played healthy in only 5 games. Rivals had zero film and slapped 2 stars on him early in the process. Jeremy Crabtree, a KC native, had every opportunity to watch film on the kid since a couple of his games were on cable in KC, but he just never had time to look at it. Eventually, Mack had some pretty impressive offers from a handful of BCS schools despite what his profile shows, but Rivals never really evaluated him beyond talking to opposing coaches before his senior year. Also, later in the process, politics begins to play into how the ratings work. Crabtree is far more interested in keeping the subscribers from the bigtime schools happy by giving their players higher ratings, and it doesn't look good when he shifts their recruits down in favor of guys from schools that have a smaller membership on their network.
I'm not saying the kid is or is not better than 2 stars, but rivals really didn't do much to evaluate him after an injury-plagued junior year. You can see why they swing and miss so often with their ratings.