The same is true for me (more than a decade of software contracts) and I also have never been screwed.
I have the feeling that the people being jerked around are doing web sites. The problem with standard web work is that (a) the competition is stiff, (b) it is easily contracted out to anyplace in world (making it price sensitive), and (c) you're dealing with the public, i.e., with people who don't know what it takes to do what you do. (My work is sufficiently niche that I deal with managers at software companies or a senior manager if it's not a software company.)
I believe that I manage to bill more in the long run by not taking a deposit. A deposit that's a percentage of the total puts the total as sharp figure in the client's mind. I bill either an hourly or daily rate, and the customer is free to change his mind on the design and add whatever new requirements he wants without worrying about re-negotiating the contract or exceeding a fleetingly discussed total.
I have the feeling that the people being jerked around are doing web sites. The problem with standard web work is that (a) the competition is stiff, (b) it is easily contracted out to anyplace in world (making it price sensitive), and (c) you're dealing with the public, i.e., with people who don't know what it takes to do what you do. (My work is sufficiently niche that I deal with managers at software companies or a senior manager if it's not a software company.)
I believe that I manage to bill more in the long run by not taking a deposit. A deposit that's a percentage of the total puts the total as sharp figure in the client's mind. I bill either an hourly or daily rate, and the customer is free to change his mind on the design and add whatever new requirements he wants without worrying about re-negotiating the contract or exceeding a fleetingly discussed total.