The standard is "liklihood of confusion" in the relevant marketplace. Multiple registrations as you mention are probably not required and would be very expensive. Beyond that, your analysis would be very fact specific and you would need to consult an attorney. Answering your last question, if you own the trademark, you can force owning the domain names, whether dot net or dot com. However, since trademark ownership requires use in commerce (except an intent to use mark) then your domain name question about non-use of the mark in commerce makes no sense, and developing a web site for a product in sale is so simple as not to be avoided.
Answered on Jan 20th, 2013 at 11:47 AM