When many people set about starting a social networking site and comparing social networking software, they often get caught up in Feature Creep.

Thinking that more is always better, they try and cram every possible feature — videos, blogging, RSS feeds, music, etc. — into their social networking site.

The funny thing is that even the people who create feature-rich social networking platforms don’t think this is a good idea.

“The main problem with feature overload is not technical – that can be handled,” says Andrew Boon, director at Boonex, makers of Dolphin. “The real problem is UI [user interface] complexity and distractions, especially on the first stages when there’s no content in some areas. ”

A good example is Google Buzz. It has all the bells and whistles, with 10 times the features of Twitter. But it’s not easy to use, doesn’t solve any real problem, and pales in comparison to Twitter in usefulness, ease of use, and popularity.

Twitter does one thing, with limitations, and it does it well. It wouldn’t be a better product if it allowed 300 characters. Its limitations are its strengths.

Boon uses the example of a community site for soccer fans. “The site needs Events and Forum sections first, and Featured Profiles for team players. Videos/photos sharing for sharing memorable moments . That means just a few modules, a simple homepage and clear site purpose message [or unique selling proposition].”

If you starts adding extra features, your users will either get lost and don’t know where to start, or their activity will be limited to a section they are comfortable with, which in turn dilutes the content and slows viral growth.

New features may have a place, especially if members request them, but add them slowly and when there is overwhelming need (not the first time you get a request).

“Some people still think that providing more options is the way to attract attention,” says Boon. “I believe that the Internet is at the stage when there are already too many options. We need things that do less, but do it better.”

Another common trap social networks fall into is slavishly following Facebook or some other existing site whenever they introduce any new feature or design.

“Our customers consistently want to emulate the innovations rolled out by the big social network players. When Facebook releases a new feature, we usually see an abrupt influx of requests for that feature,” SocialEngine‘s Charlotte Genevier told me in a recent interview. “However, our team always considers these requests critically since features deployed on huge social networks like Facebook don’t always translate well to smaller niche networks.”

So start your social networking site with the core features members need to interact with whatever the focus of the site is, and each other. Then listen carefully and observe their behavior to see where you can add smart social networking features that engage users and encourage activity.