Let me take the mention of tinyurl.com and substitute URL-shorteners in general. The answer is whenever we crawl one of these links if they do a 301: yes we do follow those and flow the PageRank as we normally would with a 301 from any other site.
Danny Sullivan did a really great piece about URL-shortening services where he took the top URL-shortening services like tinyurl.com, bit.ly and sort of said, ok, do they do a 301-redirect or do they do some other sort of redirect.
Just as we do with any other sort of 301-redirect. With URL-shortening services that do that correctly, we should be able to follow that and find the destination URL with no problem whatsoever.
by Matt Cutts - Google's Head of Search Quality Team