The whole system really is kind of ridiculous, and in general, "bad tips" and "good tips" usually average out, so overall it's not really a big deal. I've been in the industry for a long time now as server, bartender, and now manager, so I tip like a crazy person. 30-40% is usually my standard...because I just tend to keep throwing cash down on the table.
Last week my roommate (also a server/bartender) and I went to Buffalo Wild Wings for lunch. Our bill was around $30, and between the two of us we ended up leaving the guy a $13 tip for bringing us wings and a beer. As we left, we discussed how stupid that was, but we were both totally okay with doing it.