There is a User Ratings service in one of the niches I follow that provides a rating service. The concept is that multiple sites implement the rating code and thus ratings build up more quickly. The trade-off is a participating site can access the data.
At least one of the sites using the data displays the aggregate ratings in a rich snippet and it does, in my opinion, make the site look more authorative. Were a second site, third site etc to do the same, does anyone know if there is any impact on Google displaying the rich snippets - or even on ranking bearing in mind it could potentially be viewed as dupe content?
IMHO I don't think Rich Snippets wil start appearing in the broad short term due to their lack of wide spread use for notation. In looking at the concept of Rich Snippets it's something I've written about the industry needing for quite some time. It gives a more granular look at the data on a web page. It allows the page creator to specifically identify Information "X" as information X and not to be intepreted as information "Y".