It is necessary to "touch evil" a little bit now and then to learn how to be good. Producing malware can in some ways help you better understand other more productive things later. What I'm not sure of is whether or not it is absolutely necessary to create malware to gain that knowledge. It may be that creating malware make you a better coder when it comes to script engines, it can make you a very clever designer of script engines simply by knowing smart infection techniques. That's one example. Personally, I wouldn't do malware.

I would like to point out that a Viral Compressor would work without being malware. It attaches to exes and compresses them, thereby saving space and time. http://virus.wikidot.com/cruncher

I can imagine that it would be usefull to analyze certain values for debugging(similar to attach to process)