For my site (BuyersVote.com) I let people do some things (like starting a new category) without registering, but to actually vote/rate items - I still haven't figured out a way to prevent abuse without people registering.
Has anyone been able to successfully do voting without logins?
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Here are my two cents on the issue:
Imagine the country going to vote without Identity/SSN verification (registration) and only asked to put down address (IP), how many times a fraudulent person would vote? once?
Even online registration is not fool proof 'coz one can register many times using many emails, but it does create a filter to keep the spam low.
By looking at your site's name 'BuyersVote' I was reminded about a controversy associated with ebay once (not sure of now), some of the the sellers were creating bogus buyer accounts on ebay and creating fraudulent positive feedback for themselves and this was a 'with-registration' system.
So I guess voting systems today are open to abuse, registration just creates a filter and keep the abuse rate low. This will remain the status-quo till the web gets a universal, neutral online identity provider. (OpenID is there but doesn't seem to be catching enough attention and is not an ideal system in my opinion)
Yep OpenID offers a step in the right direction, but not a complete solution. I actually offer this now so people can login with an account they already have (Google, Yahoo, Facebook, Twitter, etc - this uses rpxnow.com). This reduces the hurdle slightly since they can often login with just a few clicks instead of a full registration process, but it's still a hurdle. Thanks!