Why is the ideal rel canonical URL structure?

[wepayinc]

I currently have the rel canonical point to wepay.com/donations/123456.  Is it worth the effort making it point to wepay.com/donations/donation-name-123456?  I would also need to track histories if users change the vanity URL with this new structure.

[Copstead]

The rel=canonical is based on the actual url structure.  So whatever your url structure is (your navigation), then the rel=canonical tag should match.

[NakulGoyal]

If I were you, I would recommend changing it. From what I understand people/websites using your service would be linking to you. A little bit of keyword would be helpful here instead of just the numbers. However if it's too much of an effort, you can ignore it. You need to evaluate the best use of time and resources available.

I hope that helps.

[Dr-Pete]

Agreed - the "canonical" shouldn't just be a tag - it should reflect the actual link structure of your site, or it's not going to be as effective. Adding the additional keywords to the URL could slightly boost the profile pages, but there's always some risk to making a massive change like that. See my post from last year:

http://www.seomoz.org/blog/should-i-change-my-urls-for-seo