It is unethical for a law firm to solicit a client that they know is already represented by counsel. A law firm that sends a prospective client anything in writing must clearly state that it is a "solicitation from a law firm." I don't know if that applies to internet communciations, but logically it should.
I would not trust any attorney who recruits clients on message boards, and I doubt if you or anyone else can give me a verifiable example. However, I would not be at all surprised if an over-zealous poster directed readers to a particular law firm without the law firm's knowledge or permission.
I get a lot of class action solicitations from law firms. I would imagine that you do, too, considering the junk stocks you tout.
By the way, I am not a lawyer, so pay no attention to me.