Unlikely. However, only one person can be using a given CD Key at a time on BN, so if you take someone else's, they'll know - and, if you share CD Keys, I understand, the BNet people are notifying the manufacturers so that support can be denied. They may also ban the shared key from BNet (which may be the CD Key mess-up you were refering to.)
Just go buy a copy - you'll get more hours out of it than you would an equivalent spent on movies.