How URL Redirection affects SEO?
- by Costa
The following paragraph is from SEO Google Guide 
  Google is good at crawling all types of URL structures, even if
  they're quite complex, but spending the time to make your URLs as
  simple as possible for both users and search engines can help. Some
  webmasters try to achieve this by rewriting their dynamic URLs to
  static ones; while Google is fine with this, we'd like to note that
  this is an advanced procedure and if done incorrectly, could cause
  crawling issues with your site.
What makes URL re-writing implementation incorrect for GoogleBot? I am using Asp.net 3.5 framework.
Thanks