I'm going to respectfully disagree with Robert W...
I believe that bots will in fact look at the URL, and if a key word is
in the URL (and in the actual content of the file) then it is more
likely to rank higher on search engines (for that keyword). This is
just my understanding by reading very basic SEO articles...
The WWW has changed since the original designers sent their first TCP/
IP message. For instance, that's the whole point behind DNS - so that
a mere mortal doesn't have to remember an IP address in order to reach
a web host.
Using model IDs is the easiest solution without a doubt, and works
great for "private" webapps where SEO is not a concern. If you want
pretty perma-links, you'll have to craft your routes and probably use
gsub in the process to get rid of unsafe characters such as spaces,
dots, amps, etc. Also, take a look at permalink_fu plugin which is
supposed to help in exactly this (I have not used it).