As my lawyer explained to me long ago, who eventually "wins" a lawsuit is rarely interesting. Cost, time, and agony to get there are much more relevant factors.
The "our users represent that the content is theirs" may not keep Pinterest from losing an eventual lawsuit, but it does complicate things enough that it discourages legal action. That may be sufficient for them to cash out long before the suits are complete.
Or, like YouTube, things like that may allow them to grow big enough that they end up with sufficient negotiating power that they can get away with quite a bit, and possibly reshape what's considered reasonable.
The "our users represent that the content is theirs" may not keep Pinterest from losing an eventual lawsuit, but it does complicate things enough that it discourages legal action. That may be sufficient for them to cash out long before the suits are complete.
Or, like YouTube, things like that may allow them to grow big enough that they end up with sufficient negotiating power that they can get away with quite a bit, and possibly reshape what's considered reasonable.