I don't anticipate this being a big problem but I'm curious to know if a line needs to be drawn to keep micro brewing (large batch brewing) out of the site. I don't really see a lot of harm in allowing it but then again it may be a slippery slope.
In much the same way that amateurs and professionals coexist on Stack Overflow and the other stack exchange sites, I don't see this being a problem at all. We all have much to learn from and teach to each other.
I think it would be better if this forum was simply "Brewing". I don't think there will be many messages from anyone other than home brewers, but I see no need to limit it.
Years ago, on the newsgroup rec.crafts.winemaking, I remember a few messages from a guy who had started a very small winery. Those messages were interesting and it would have been a shame if something like that happened here and the pro brewer was booted out for not being a homebrewer.
I don't think anyone should be excluded. Many pro brewers started out as homebrewers and got good enough to earn a living from it. We can certainly benefit from their knowledge to learn and improve our brewing efforts.