One of the worst mistakes:
not having up-to-date whois information, so that you don't even get renewal E-mails from the registrar and find out some day that you lost the name (BTW monitor your names and do not rely on the registrar reminders).
Would tend to agree with you on that one-fortunately I stopped short on one domain which they supposedly registered for me but is in someone elses hands.I will not register or trade any names listed with them.
My biggest mistake has been to not register a good name when I find it. This has happened several times. It's really annoying, especially when you delay registering a name for a few days because you figure no one else could possibly be doing the same searches you are.
Of course not knowing what a good name is and registering any crap as soon as you find it is also a mistake