I'm not sure about the class size, but after you are elgible you get 20 (one way) buddy passes per year. They are pretty much useless though because the majority of our flights are either full or oversold and you sit on standby. If you "need" to get somewhere you are better off to buy a confirmed seat on a low cost carrier. Each way on a buddy pass will cost you $52.50 (domestic). Normally when I travel with my g/f or friends I have them buy a cheap seat on Southwest for $49, that way we know we will make it to our destination
Hope that helps!