Ask HN: Are search engines indexing short-urls?
Any idea how to fix this? Specifying rev="canonical" maybe?
Any idea how to fix this? Specifying rev="canonical" maybe?
Next you can look what kind of redirect the service is using: status code 301 or 302 or something unusual like 307. Rex Swain's HTTP Viewer is a nice tool to find out the status codes: http://www.rexswain.com/httpview.html
A site: search on Google for the domain of the service may also be interesting.
I have seen that Googlebot and other crawlers will also follow "nofollow"ed links, I suspect that they use these links for page discovery like ordinary links. The nofollow attribute just tells the search engines that this link can't be trusted and shouldn't be considered for ranking calculations (like PageRank etc.).
It is not clear how much value Google and other search engines give to a link that goes through a redirect. Sometimes pages redirecting with the code 302 appear in the search results instead of the target page (302-hijacking).
The link: operator is broken, it shows you only a small selection of links pointing to a site if anything at all. The Google webmaster tools show more links, but not all of them. Yahoo Site Explorer shows more links: http://siteexplorer.search.yahoo.com/ I have seen nofollow links in both of these tools. They do not tell anything about the value of a link.
I remember that I have seen links from tinyurl in the old version of the Google Webmaster Tools.
As for short URLs, they shouldn't be designed to steal page rank. If they do a proper 301 redirect, then the original address should receive the SEO value.
For Twitter specifically, remember that lots of websites syndicate tweets, links and all. It's likely a crawler would discover the links on non-twitter.com websites.