I think martinibuster may have initially been looking for examples from the general web developer/SEO/SEM types who also do SMO. I believe you may be reading way too much into the question if you think he is suggesting a policy change at WebmasterWorld. As per the TOS let's keep that discussion out of public threads.
Also, we've been able to discuss SEO and SEM topics for years while avoiding specifics and self-promotion. I'm confident the same can be done for social media topics.
Back to the topic at hand...
As per the OP, I don't think I can relate any huge success stories in my use of Twitter on the sites I manage. Sure there is some extra traffic and a bit more interaction with customers, but nothing tectonic.