httpwebwitch - 2:22 am on Jan 2, 2011 (gmt 0)
Why would they sue you for it? Would you for some reason hold it ransom or refuse to transfer it to the company?
If you owned the domain before starting with this company, and it's a hot dot com with resale value, then you could negotiate a sale. This company earning millions annually can afford to toss you a few $G for a domain that you had, in essence, loaned from your personal collection.
On the other hand, if the domain name was registered with the intent to be used by the company, then you were acting on behalf of the company when you acquired the registration, just as you were when you worked for free for a year. It's reasonable to assume that acquiring a domain was a necessary task among your web development duties.
If you're getting 10% of millions annually, I don't think you have much to complain about, and you certainly don't have any reason to withold a domain name that is clearly theirs, even though it's your name on the registration.
IANAL, but if it comes to a head in court, yes I believe they could sue you for it, and win.