Users will start to think about where they contribute, and with what. That will make it harder to create valuable sites based on other peoples work, but it will not stop such sites from becoming successful.

This is the way the world works, it’s nothing new. Everyone wants in when something suddenly gets valuable. The problem is that this is hard to know up front. Besides, it’s hard to become successful, otherwise everyone would have been at the top.

Sites that base their content on productive users will probably have to start producing a lot of the content themselves. If they are successful, others might want to join in, but the best users will learn their value and ask for more before joining in.

As you put it, it’s likely that artists helped in the growth of Bebo (and that deserves something). It’s also true they also got something out of it (hopefully public awareness).

But, if we take this analysis to other examples, it doesn’t seem to hold:

1) should google paid people for their content? After all, google is making profit of content created by others….

2) should you pay me (something) for this comment? This comment is content, is helping develop a comunity…

On the end, the only thing that seems reasonable is to consider that (likely) Bebo had a TOS and artists accepted it… And i think that if another model surfaces that better appeals to both business owners and users, then it will rapidly grow and wipe (or force to change) the rest.

Cheers.