I've done technical support for a good chunk of my life, and I've begun to see some trends in the type of people who require technical support. Keep in mind that the majority of my tech support career has been for ISPs. In any case, here are my observations.

Mumblers
They mumble. I think some of these people actually have the telephone between their teeth while they're talking. This also includes the sub-category Eaters, who love to chomp, chew, swallow, and gargle while they're talking to you, and the Foreigners, who don't speak a lick of English and expect you to help them re-configure their foreign-language version of Windows.

Apologizers
I'm sorry... I'm sorry... I'm sorry. My computer is slow. I'm computer illiterate. I'm typing one-handed. My fingers are all broken and I'm typing with my toes. Really, we don't care. As long as you do what we say, we don't care how long it takes. Now shut up, because you're ruining my call averages.

TriggerFingers
They click on EVERYTHING. It doesn't matter where you tell them to go, they click on something else. They end up in the obscure depths of their operating system, and can't get out. Just... let... go... of... the... mouse... ma'am...

Explainers
It takes hours to get through calls from these people. They like to explain the problem in explicit detail, and won't shut up, even after you've fixed their problem. These people love to read off ENTIRE error messages, including cryptic error codes that don't mean a thing to anybody. And ooooh, MAN do they get mad when you interrupt them!

Know-It-Alls
Out of all caller categories, these are probably the ones we hate the most. They THINK they know more than you. People don't understand that we've done what they're trying to do HUNDEREDS of times, and they're doing it ONCE. That makes us the experts. Just because you know some obscure fact about computers doesn't mean you know everything. This is our job, don't tell us how to do it. And don't question what we ask you to do. If we tell you that Fdisk will fix your problems, then dammit, FDISK!

The Nerds
People from this category often exibit the same traits as the Know-It-Alls. Unlike the Know-It-Alls, these guys actually know what they're talking about. Usually they know more than we do. Everything would be okay, except that they never have normal problems. They've already gotten everything working fine, and now they want to know how to exploit their service. "Yes, I'm trying to hook up a peer-to-peer connection so that I may turn on my next door neighbor's toaster in the middle of the night. Can you help me?"

Multiple Personality
These people are very sweet and do what you say and are generally nice customers. There's one catch, though. They have kids, or a signifigant other, or a dog, and they YELL at them. Most of the time, they forget to pull the phone away from their faces before they yell. This gets on our nerves very quickly.

Rednecks
"Uh, I'm tryin' to hook my 'puter up to my hog, and it just ain't workin!" We find these people funny. Especially when they tell us that "the internet broke". Amazingly enough, this category often overlaps with The Nerds. The only difference is that The Nerds are trying to do these things on purpose.

The Psychos
We never really figure out what causes these people's problems. We just listen to them yell. Usually their problems involve fire, electricity, and melting things. These are the kind of people who download viruses just to see what they'll do. Then they expect us to fix it. Most of the time, they're either drunk or stoned while troubleshooting, which makes calls very interesting and sometimes humorous.

The Oblivious
These are the people that go years without realizing what the right mouse button does. A techie friend has set up their computer so they never have to see the behind the scenes stuff, and when they finally see all the settings, sub-menus, and registry entries, their brain collapses. It's usually best to not try to explain what you're doing to these people, just say, "because that's the way it needs to be -- it's magic." Most of the time, the Oblivious are more than happy with this answer. Many of these calls degenerate into explanations of "How the Internet Works".

The Misled
I really do feel sorry for these callers. They've been told something by a Know-It-All friend who calls himself the local "guru". In reality, that Know-It-All knows NOTHING, and has given his friend very, very bad information. People from this category often manifest themselves in the form of hysterical, crying women.

The Paranoid
They won't let you do anything to their computer without a full explanation of why you're doing it, because they think you're setting up secret government software that lets you spy on what they're doing on the internet. Most of these people are just afraid you're going to find out about their 35 gigabyte porn collection.

The Dependant
These are my personal most hated customers. They do business using their computer. When their software stops working or their internet connection ceases to function, their fragile world comes tumbling down around them. These people have never called into tech support without shouting their lungs out. It's never their fault that they didn't back up their hard drive. It's never their fault that they don't have a second email address in case their first inbox gets corrupted. It's never their fault that they forgot how to use a FAKKING TELEPHONE. No. Of course not. It's always our fault. If you're gonna depend on your computer, learn how to use the damned thing.