There are many good reasons to be involved in
Wikipedia:
- It's fun.
- It's easy.
- It's educational.
- It's social.
- You are part of an exciting development making use of the open source idea.
- You can correct other people on the spot without asking their permission!
- It's exciting. Wikipedia has created literally thousands of articles in the mere year and a half since its inception--more than 2,000 per month, in fact.
- It's interesting to share your knowledge with other people, particularly knowing that others can instantly edit or react to what you've written.
- To contribute is to gain.
See also why Wikipedia is so great.