I obtained webbcard.net (extra b). There is a website webcard.net out there. Am I asking for a lawsuit? Any way to minimize future trouble besides picking another domain?

My site would be totally different model/topic than the one currently existing.

I doubt you'd have problems with doing this.. if you aren't a direct competitor, chances are they won't give you a hard time about it. (Chances are they won't even realize it exists!). Just an example to throw out there, shell hosting companies acquire domains similar to providers such as Cogent, Internap, heck even Switch & Data. They then use these domains for vhosts to "look cool" on IRC and such. I don't think you have anything to worry about.

Interestingly enough, it looks like webcard.net is actually doing exactly the same thing you're worried about. It looks like they try and capitalize on misspellings of webcar.net.

I wouldn't worry about it if I were you.

I also don't think you have anything to worry about.

unless they own a trademark on that name, there is no issues

especially when its owned by a domain speculator :D