Every so often, a big company realises they need to provide their customers with a platform to talk to each other.
It's tempting to launch big, promote heavy and ramp up to 80,000 registered members. I think that's a mistake. The outcome can be a mess that drives either newcomers or existing members away. Here are two different approaches:
1) Launch Elite: Use the big company's connections to recruit the most elite and highly regarded community members possible. Make this a community everyone else wants to join. Then let these people decide who else they want in and the structure.
2) Launch niches: Launch by area, topic, or any other niche. Then go about connecting the niches to each other.
Start small, get the right interactions, the right structure and grow steadily.