A problem on dynamic driven websites is the URL, very often is it way too long (I found some with 151 characters). How many characters can the spider read?
ciml
5:09 pm on Jul 5, 2002 (gmt 0)
This ODP category [dmoz.org] has a 160 character URI, or 153 character URL. The low PageRank is just because it's a lot of links from the Google home page.
The problem with some dynamic sites is the use of ? and & characters, which makes Googlebot less keen to spider them (though it still can do with enough PageRank).