I am splitting my local classifieds site into 500 subdomains.... will this in anyway harm the site for search engines? TIA.... James.
Since subdomains are seen as seperate sites by google it may have negative effects in the short term. Make sure that you do redirects from the old sections of your site to the new subdomains. In the long run, the multiple subdomains will probably help you. Since you can link them together and use them to boost each others rankings.
...except if you overdo the linking from the same IP it can be considered spam and get you blacklisted!
Indeed, pretty much any SEO technique can be considered spam if done in excess. -- Always use in moderation and be sensible.