I don't think i have ever paid for shareware. In most cases, i won't even download it if it isn't freeware. If i do download it, it's probably just for the free-trial, and then delete it. There are times though that i have used a crack or serialz. But i've never really paid for it. IIRC, i did but the upgraded versions of SecureCRT (before i knew of PuTTY), VMWare 1.0 (before it was free), and Forte Agent 1.0. Except for VMWare, those were solid programs for a decent price. Even VMWare was good, until it trashed my disk.
In other cases, i used a program long enough where i thought to pay for it, but i just switched instead. I figured i should pay for Windows, so i switched to Linux (eventually going back on another computer, because it was given to me, or to play games), or WinZip, but version 7 (iirc) just came out and it was so bloated and used the ugly flat buttons that i immediately switched to ICEOWS, which works pretty well.
Now and then, however, i run a program that really helps, and i think "i should send them five bucks". If it's a cracked version i'm using, i don't bother because it's too much trouble. If it's shareware it's probably less than what they want, so i figure it isn't worth trying. If it's freeware, it's usually too hard to track the person down. Or at least i'd like to think so.
Then came Spybot - Search & Destroy After saving a friend's (no, seriously) XP setup, i think i sent him a few dollars via paypal from that link on the side. I spent hours on cleanup, and the final stage was beyond me. Between it and Process Explorer (kill process tree) i could finally do it. I'm pretty sure i sent some cash. I know i wanted to. And, if i really need it again, i'll probably send a couple dollars here or there.
Today, i just used FileMon to track down a file being used by a project. Between IIS, virtual directories, SharePoint Server, and hardly commented code, i hadn't the slightest idea which file was being served. (The virtual directory had a blank vbs file in it.) With FileMon, entry 3151 showed me the actual file being read. And that when i thought i should send a few bucks to them (not Microsoft). No link though.