Services like Caviar, Postmates, and Eat 24 (now part of the Yelp empire) are increasingly becoming a vital part of fast-casual restaurants' revenue streams. But as the Chronicle discusses with several of them this week, all that convenience for the customer comes at a price for the restaurant, either as a chunk of their profits, or just in the loss of face-to-face interaction and quality control.

In terms of profits, Caviar may be the worst culprit in that they take 20 percent off the top of every order. Nate Pollak of American Grilled Cheese Kitchen tells the Chron that online orders now account for about 30 percent of their daily business, and between those commissions and credit card processing fees (3.5 percent), they're profits on all those sales are disappearing, and will mean they have to raise prices on their grilled cheese sandwiches.

Postmates doesn't charge a commission to restaurants, instead charging a 9 percent service fee to customers, so it's therefore mostly a win-win for restaurant owners. The only problem is they're sometimes handing off their food to random jokers and have no control over what state it might arrive in at the customer's door.

Says Christian Ciscle, the owner of Wing Wings in the Lower Haight:

"We’re out of the loop. It’s like Uber. It’s a bunch of randoms delivering food. Anybody can do it,” he says, pointing out that while most delivery people are professional, others might pick up an order wielding a cigarette or even show up barefoot.

Last summer I was speculating that there'd be some shakeout in this online delivery realm, since services like these, and Instacart and Spoonrocket, sound a lot like bygone businesses of the first dot-com boom like Kozmo and Webvan that bit the dust in pretty spectacular fashion. But, business-wise, maybe this new generation has it all better figured out, and they're tapping into a need we all have to be lazy and not talk to anyone on the phone — not to mention providing delivery people for restaurants that wouldn't otherwise have them.

Related: Are Caviar, SpoonRocket, And Instacart Doomed To Go The Way Of Kozmo And Webvan?