Some sites supports RevCanonical link for self hosting short URL. Such as flickr, php.net, dopplr.
For my understand and some articles also said that. URL shorten service should use 301 permanent redirect instead of 302.
But all the websites I lists above is using 302 temporarily redirect for their RevCanonical link.
Here are some result I got using curl -I
Dopplr:
> curl -I http://dplr.it/explore/0xd1 [0:57]
HTTP/1.1 302 Moved Temporarily
Server: nginx/0.5.33
Date: Fri, 04 Mar 2011 17:21:33 GMT
Content-Type: text/html
Content-Length: 161
Connection: keep-alive
Location: http://www.dopplr.com/dplrit/explore/0xd1
Flickr:
> curl -I http://flic.kr/p/9m9Cmj [1:21]
HTTP/1.1 302 Found
Date: Fri, 04 Mar 2011 17:29:43 GMT
Server: Apache
P3P: policyref="http://p3p.yahoo.com/w3c/p3p.xml", CP="CAO DSP COR CUR ADM DEV TAI PSA PSD IVAi IVDi CONi TELo OTPi OUR DELi SAMi OTRi UNRi PUBi IND PHY ONL UNI PUR FIN COM NAV INT DEM CNT STA POL HEA PRE GOV"
Location: http://www.flickr.com/photo.gne?short=9m9Cmj
....
I don't understand why this case(self host shorten URL) should use 302 redirect. Can anyone explain the reason?