I think what Ive been hearing from people is mostly that you dont want to try and sell to people directly through Twitter.

Nor do you with Facebook, but a Facebook ad...thats a different story. You probably know by now that its in bad taste to just post updates with your marketing message all the time. Like Brandon Eley of Kelsey said in an interview, you have to know the rules of the community, and Facebook and Twitter have unspoken rules that just make you look bad if you engage in this kind of activity.