The point about paid links and spam report is that Google is already able to understand which links are paid and which not. And Google is already devaluating paid links.
Asking users to be a spy on paid links won’t work too much. Yes, ok, someone in the world knows for sure about a website who’s buying/selling links, but most of them can know about links only if they are involved. They should admit “I buy links” or “I sell links”. It won’t happen, of course. And most of spam reports about paid links will be just undemonstrable.
Google won’t be able to know about tons of paid links. As long as you don’t use Google Checkout to pay/cash or Gmail to negotiate…
But they are pushing SEOs to most sophisticated paid links. For example, no links on footer anymore, but instead put a link with the right anchor in a paragraph that speaks about the right topic. They already work better today. And tomorrow we’ll see much more about this phenomenon.