I currently develop Ecommerce applications in Perl (with some other stuff mixed in), but I'm considering a shift to Java. The reason: more secure, simpler tracking. I recommend the use of sessions instead of cookies b/c I'm a believer that even if you put a cookie out there, someone can alter it or read it, and you likely don't want that to happen. The safest you can make things from cracking, to me anyway, is to keep that data on the server and just give the users a "pointer" to that info.

But then, I haven't actually gotten into using Java in this way, so I'm sure there are other challenges. And certainly Perl's faster to develop than Java/JSP's, and easier to troubleshoot.