This is really annoying. I recently printed 5000 6x9" flyers through SoBeGraphics.com, and they did a couple of things that seemed really shady. I found SoBeGraphics in the back of Photoshop User magazine.
First, I was promised delivery by a certain date, which would not have happened had it not been for a circumstantial call verifying the shipping address. So I had to upgrade my shipping, costing me $40 extra (they refused to pay for it, despite the fact that it was their broken promise).
Second, they stamp each flyer they make with a blurb that says "SoBeGraphics.com - 1.877.ASK.SOBE". Upon later perusal of their website, I discovered this fact in the fine print on a page that you would never read when placing the order. This sort of thing is fine if they make it explicit that it is their policy, but I'll bet that most people are thorougly surprised after receiving the product (as I was). I would gladly have paid the $50 extra to remove their stamp from my flyer, anyway -- had I known.
On the other hand, the quality of the work is good. So my summary after working with them for the first time: good product, broken promises, and the shady practice of getting you to inadvertently market their business for free. I will never use them again.