Ah yes...when I first saw this thread I thought to myself "nah, don't read it...you'll just get caught up in it". Alas, my boyfriend and I couldn't resist and now I feel the need to respond.
First and foremost, I think I have reluctantly accepted that people are going to tip how they think they should and no amount of yelling, fighting or arguing on this board or elsewhere are going to change some people's minds. That still doesn't stop me from wanting to drop a few of my own thoughts.

I think the funny thing is that I have yet to see a former server/waitress/waiter ever tell me that they won't tip at least 15%. I think it's because after you've worked in the industry (actually on the floor waiting on tables) you understand the ups and downs that every night can bring. I personally watch for things like a server who might have a large party or an unusually large section of tables. I look for that table with screaming kids or the punky teens who I have a creeping suspicion will not leave a big tip. And yes, it is just who I am...to take these things into consideration when I determine what my tip will be. Take my boyfriend for instance. He works at one of the largest and busiest restaurants in the city of Chicago...and if you've visited here you likely know what I'm talking about. He will often go out of his way to take care of children (he brings sliced bananas to the tables for families with young children) or large parties. And yet bamm...you can do everything in your might and people will still leave 10%...maybe 15%...or sometimes in his case $1 on a $100 bill. And no, it's not because he's a horrible server. Quite the opposite really and it's not because I'm biased....
So yes, there are some out there who argue that you will tip based on service received...but that is obviously a very subjective matter. But he (nor I when I was still a server) doesn't discriminate based on the table and whether he "thinks" he'll get a good tip. Everyone gets the same. So then, take a day when you consistently do your best and people still leave maybe 10 or 15%. Guess what, at this particular restaurant if you leave the bus boy anything less than $25...you'll get in trouble with a manager. Then you have the bartender and food runner to tip out and maybe even the dessert person if they had to make a bunch of desserts for you. It doesn't matter that you had lousy tips all day. You are still expected to tip out a certain amount. So to the person who leaves this minimum 8% that the govt makes you claim...shame on you (which btw has since gone up...the government now expects that you are WALKING HOME with 10% of what you sold). At most restaurants that have a bar or busboy, you have to give at least 3-5% of what your SALES were (no, not your tips, what you actually SOLD in food and drinks) to someone else...and sometimes a lot more than that.
I relate this story not to bore you (although I probably did for some) but to maybe shed a little light on this issue. For instance, many people probably don't know that the standard hourly wage in IL for servers is $3.09 an hour. You do not get a raise after so many years of service nor do your wages go up if the restaurants raise their food prices, as another poster suggested. In fact, at one Chicago chain servers actually make $2.64 per hour because the management automatically charges them 45 cents per hour worked for bread and soup...regardless if they ever even eat the stuff. And I'm sure there are just as many nuances all across the country. I for one didn't know that servers in CA made so much more than their IL counterparts...but that doesn't mean I'll tip less when I go to L.A. in January.
So then you could say hey, this is all great stuff...but it's not my problem that the restaurant industry is in such a state. Well let me tell you something...if we went to a European mode, as some suggest, service would go down the tubes my friends. The attitude of Americans differs so much from Europeans (and trust me, I've spent enough time in France to know) that it just would never work. People are already complaining about an automatic 15% gratuity. I do think it's the American way to be given the freedom to choose your tip, but that 15% for certain number of parties is because 1.) big groups can't always handle the math and 2.) a server has likely put a lot of time and effort in that table vs other tables they had...the restaurant wants to make sure they get compensated at least somewhat...otherwise I GUARANTEE you it would often happen that people would be left 10% or less...and not even based on bad service but simply because some people are cheap (refer to the poster who had the friend who left $1.50). But you should do so in an informed manner, not because you're afraid to part with those hard earned dollars. I'm a college grad barely making it...and my boyfriend and I have been saving for this trip for a while now...but that doesn't mean that we would ever think of not tipping someone an acceptable amount because we don't want to part with our hard-earned $$$. If you want the service, you need to pay for it.
And wee hagis...well, I've actually tempered my reaction to your posts...but let's just say that you if you are so intent on getting adequate service for what you're willing to tip...I suggest that you try putting out what you think will be an acceptable tip on the table BEFOREHAND next time...and see what happens to you.