The best way to get rid of stupid posts is to ignore them, whether they have a name on them or not. Seriously, how long does it take to skip over a "Yay!" thread. I actually initially saw those threads as kind of funny and sarcastic. A lot of time there are "so and so hit a homer, YES!!!!!" threads. I get as tired of seeing those as i did the "Yay! ....." threads, thus i found an ironic humor is those posts. I then skipped over them, found threads in which I was interested, and read and posted accordingly. No big deal.
Guest is kind of a trial period. Once people get used to a certain board, they usually assimilate to the common communication level of the site. Idiots, in the long run, weed themselves out.
I really don't think any of this is a big deal. As the Cafe grows, we will see these things. oh well.