I think lawsuits happen anytime there is big money to be made. Goldman, Morgan Stanley, and Facebook have hundreds of billions of dollars. They can settle for tens or hundreds of millions of dollars without batting an eye. That pays off for the lawyers and potentially the claimants in a life changing way.
I work in this business. Lawsuits against big banks do happen all the time for stuff like this, you are right about that. But "They can settle for tens or hundreds of millions of dollars without batting an eye." is absolutely not true.
These big banks are very aware of their legal exposure and do a lot to minimize it. A bank (even a big one) would not authorize a legal reserve in the 10s of millions without lots of people very high up in management being involved. Big reserves like this are routine, but significant.
I doubt this occurs in most IPO's which see a decent pop in the price. There tends to be many fewer lawsuits when everyone involved is raking in the dough.
