Interesting that you guys brought this up. I have a literature degree, and I consider myself a reasonably good writer. Recently I wrote and submitted ahastily-written article to a fellow webmaster. The article had several mistakes and wasn't very good. I was surprised when the webmaster sent it back to me with several corrections and a "Do better next time." note. That's when I realized my writing has gotten sloppy.

Turns out this particular webmaster was a former newspaper editor. You never know who's going to be reading your site, but if you're targeting a presumably affluent audience, then you're also targeting a presumably literate audience. (If you're targeting people with no money, then this might not be the right industry, since gambling is more profitable when your customers have money.) And a literate audience will definitely begin to question your credibility if your writing is rife with errors.