Now, Firesheep was an important, and arguably justified, experiment in that it brought the perils of not using SSL over public wifi (a problem that's been around for years) to public attention by making it quick and simple to demonstrate. However, I fail to see a real justification for this. Of course, people have the right to make and distribute this software, but it feels a bit irresponsible; the source link seems to only superficially warn against illegal use, and the capability to hijack any cookie (instead of just the well-known services) doesn't seem to serve a useful non-illegal purpose.