I started coslinks because I wanted to start using del.icio.us, but when I finally got around to trying to create a del.icio.us account about a year ago, I found that someone had recently grabbed the name "cos". I hate to use any public or social online thing where I can't be "cos", so I gave up on del.icio.us, but I wanted to post & share links like that, so a few months later I started coslinks.
Now that I've been posting links as "coslinks" for 8 months here on LiveJournal, I thought about del.icio.us again and realized I wouldn't mind being coslinks there, too. So, for the new year, there are now two coslinks - the one here on LJ, and http://del.icio.us/coslinks. On LJ I'll still limit it to the links I want people to see. On del.icio.us, I'll add a lot more - just about anything I read that I may want to find later, or tag for the community for whatever reason. I'll probably also slowly add many of the links I've saved over the years, because it looks like a better place to save them than a text file, and tags perhaps more useful than grep for finding them.