Have you narrowed down the professors you want to work with in each program? Do you know if they are accepting students for next year?
One of the things that you need to be aware of is that it's common in interviews to ask prospective applicants what other programs they applied to. They do this, in part, because they want to know whether you're serious about their particular area of research. If you apply to a lot of programs with a variety of research fields, you run the risk of looking like you don't really know what you want to do. It can make you look disingenous if you say in your personal statement that you really want to do research in a particular area, then to say you applied to another university that doesn't have anyone on faculty specializing in that field. Professors know their colleagues and competition, so make sure you know what you're doing when you apply to that many programs.
If you have found genuine research match at each program, and you are still having trouble narrowing it down, ask yourself, would you pay for airfare, hotel, car rental, etc. to go interview at that school? Could you see yourself living where the school is for 5 or more years? These things should be the last things to consider in deciding where to go to applyl, but if you can't see yourself moving to a particular place save yourself some money and don't apply to a school there.
To end on a somewhat positive note, most letter writers aren't going to care to much how many programs you apply to. They will write one letter, and customize it for the programs that they know something about or know someone on the faculty. Asking for seventeen isn't going to be much different to them than asking for five.
