ROBOTANK While I realize your point about user accounts is valid and that there are potential issues with applications phoning home (I don't really know anything about where OS X security is heading, so I can't judge that comment), consider that many, or even most, users don't know and/or care enough about their operating system or its security to bother with such concerns. Learning about UNIX permissions and creating multiple user accounts for different tasks simply aren't things that your average Mac user is going to do. Casual computer users like things that work with minimal effort on their part, and Sparkle does just that. Admittedly, it's only simplifying an already fairly simple process in most cases, but it is still a convenience and a time saver, and so people will continue to like it and use it. For your own part, can't you simply disable automatic update checking in apps with Sparkle and update them manually?
(Version 1.5b6)