Comet Cursor is a program to change the mouse pointer to custom shapes on affected web sites. It is infamous for being one of the first programs to stealth-install and for tracking viewing habits.
Since the tracking only occured across partner sites the intrusion into privacy by the original CometCursor was minor (comparable to third-party ad network banners), as the company rightly argued. However newer versions have added other features.
(You may like the idea of custom pointer shapes, but CometCursor now drags in an lot of unrelated stuff with it. Incidentally in IE6 you can now use the standard CSS2 property 'cursor' to define a custom pointer shape for a web page - no extra software required.)
CometCursor/Shop was a release including a 'shopping cursor' feature.
CometCursor/Plus is a newer variant without this feature but with more toolbars, search- and search-results hijacking.
CometCursor/Toolbar is a version with only the toolbars, no actual pointer-changing features.
There are many older versions of CometCursor which have not been tested.
Often installed through ActiveX on partner web pages - used to be very widespread, but this practice has waned after all the bad press. Some software (notably Real Networks's) also stealth-installed older versions.
CometCursor/Toolbar is bundled with twistedhumor.com cartoons.
No, though using a search engine causes a pane with links to Comet's search engine (with pay-for-placement links from search company Overture) to appear.
No significant privacy violation known.
None known; there is a self-update feature, but it should prompt the user before executing code.
None known in recent versions, apart from causing IE to start up slowly in some cases.
Should be removable through 'Add/Remove Programs' in the Control Panel.