Which itch does a gravatar scratch?

This is a very serious question: I've seen lots of threads here about gravatars but I couldn't find and answer to this question: what computer identification/authentication (?) problem, if any, are gravatars supposed to solve?

Neither the Wikipedia entry nor the official website are very useful. The official website mentions a "globally unique" picture. Unique in what sense? As far as I can see it's only the hash that is unique: two persons can have two pictures looking very similar if not identical.

Note that this question is not about which problems do gravatars unarguably cause (like leaking 10% of the stackoverflow.com accounts email addresses like discussed here : "gravatars can leak email adresses" ) but about which authentication (?) problems, if any, are gravatars supposed to solve?

Is the goal just to have a cool/funny/cute icon and save bandwith by having it stored on a remote website or is there more to it, like se开发者_开发问答rving a real authentication purpose which I'd be completely missing?

Note that I've got nothing against them and find them rather cool, but I'm just having a hard time figuring out what their purpose is and if I should care or not about them in the webapps I'm developping.

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It's not a security thing. The purpose is just to give people pictures which (1) identify them easily in a discussion (barring very-unlikely collisions); (2) are persistent between sites; and (3) require no marginal effort whatsoever on the individual's part.

My impression is that they were written rather fast and for fun, and were way more successful than the creators anticipated - hence the bugs/issues. But I could be wrong about that.

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I like them for their convenience. Along with OpenID and associated login methods, uploading a profile picture is just one less step I need to take when signing up to a new website.

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The Gravatar home page explains it quite succinctly:

Your Gravatar is an image that follows you from site to site appearing beside your name when you do things like comment or post on a blog.

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CPAN Search automatically looks for a gravatar associated with an author's cpan.org address, as you see in my author page. The website, however, doesn't have to include any features for me to upload or change a picture, and I can use the same picture for other services. I can simultaneously change all of them without visiting each site.