First things first: I think the idea of mandatory tipping is completely ridiculous.
Now before you get all up in arms, know that I've seen both sides of the tipping spectrum. I worked as a food runner in a restaurant in Hawaii for over two years, so I've been stiffed and overly compensated, and no matter the outcome, I was ok with it all because I understood the wages I was hired into. What I wasn't ok with was seeing waitstaff complain, day in and day out, about customers' bad tipping habits, despite grossing a much higher hourly wage than they'd originally signed on for thanks largely to those "bad tips." Should tips be common practice for service industry employees? Absolutely not. And the idea that extra compensation is outright deserved for the nature of the work is, in my opinion, total crap.
Why are we obligated to tip? Many say people rely on tips because they make less than minimum wage. In Hawaii, minimum wage is $7.25; I was paid $6 per hour. If I received just $1.25 in tips per hour, I would be at the minimum level. And while I, like others, often received much more than this, boosting hourly wages substantially, many still complained when tips were nonexistent.
My brother-in-law was a waiter at the Four Seasons hotel in Hawaii. He made $15 per hour, but due to the high profile customers' tips he was reporting upwards of $80,000 come tax season. When a customer stiffed him on a bill, though, you can bet he was beyond upset.
This arrogance that tipping is required for service is ludicrous. I've seen a waitress intentionally give bad service to Japanese and Australian customers because she believed their nationalities were synonymous with bad tipping. I've seen a coworker approach me at my dinner table (while I was eating an anniversary meal with my wife at the restaurant I worked in) and complain about the $25 tip I left him for a $90 tab; he said it was insultingly low.
How much is enough? If you don't like working for minimum wage or less, don't work in service expecting more. McDonald's servers don't receive tips, yet they have similar duties. Teachers don't receive tips, yet they provide services much more valuable than that of your average waiter. If you get a tip, be proud knowing that your efforts to go above and beyond to provide an exceptional experience were met with reward. And if you are served by someone like this, by all means tip. They likely deserve it. But don't feel like you must shell out more dough because it's the accepted norm.
Ultimately, they're being paid to do a job like everyone else. Whether they're shoveling snow or delivering crappy food, they knew the hourly wage when they signed on. My message is this: Get off your high horse and do your freaking job.