As someone who has worked in restaurants for over 15 years, I definitely have some opinions on this subject.
I work at Outback, and our Take-away people do quite a bit. Obviously they take the order, write it down, key it in, box the order up, process your payment, and then most often deliver the food to your car. I think that our people in TA should get about 10%. They certainly don't deserve the kind of tip you would expect if you were serving a dine-in customer, but I think what they do still deserves something. I think it's really messed up when someone has a large $100+ order, which requires lots of work to put together, and stiffs the TA server, that's just not cool.
Also, there's more to taking someone's order at Outback or an equivalent restaurant, than taking someone's order at Taco Bell or whatever.
To whoever brought up the fact that they don't like the fact they're expected to tip more on a higher bill despite no more work being required of the server, just keep in mind that in most places, the server has to tip out a certain % of their sales to the bar, host, bus, etc.. At Outback, for example, 3% of my sales go to what we call "tipshare". So the two assfuck tables I had on Saturday night who decided to tip me nothing ended up costing me about $4 out of my pocket to wait on them. Thanks, dicks.
I'd better stop there, before I go into a full on tipping rant.