In a Google Webmaster Help thread, Google's John Mueller said Google mostly ignores Web 2.0 links, specifically calling out Pinterest, YouTube and others.
We're already mostly ignoring those links (just like we're ignoring the "web 2.0" / Pinterest / YouTube / article / etc links), but if you see them and want to make sure that they're not causing any issues, disavowing them is fine.
Yea, most of the "Web 2.0" links are nofollowed anyway, which is why Google is ignoring them, because they are being instructed to do so.
Most links on YouTube, Pinterest and so forth are nofollowed. But John also say "article" in his example.
In any event, figured I'd share this comment from John more widely.
Forum discussion at Google Webmaster Help.