While it generally makes sense to enrich data on websites with such metainformation, Google made the idea much less appealing to us when they decided they'd steal our merchant reviews in order to display them on their (competing) product search / price comparison pages. Who wants to become a pure content provider (with mostly Googlebot traffic) for Google's future cash cows?

Don't get me wrong - I'm very much in favor of accessibility and mashing up of publicly available information, it would greatly benefit everyone if this was easier. But I'm not going to follow a trend (and instructions) set by a monopolist who has only his own revenue in mind and strongly opposes similar openness for his own data (all of which is actually collected from elsewhere...).