Since you ask for some opinions, thought I might offer a few ideas.
-Most of the complaints are about paying to watch a sale, which has nothing to do with bidding. Require them to register to watch, but do not charge. If they want the option of bidding, then have additional steps for that.
-To validate a bidder, require registration 24 hours prior to the sale. Once you have been validated, have the information updated every 30? days in order to remain an active bidder. Yes, this will decrease the number of impulse bidders, but once you get the bidders trained to register early, all will be fine. If I go to a live auction and sign up for a bidder number, do they "validate" me before the sale? I don't think so.
-Do not charge to register to bid. That seems logical to me, why should you expect anyone to pay for the option of spending money?
-I am sure you have problems with people buying then not paying, so you get ONE chance, if you screw up once, you are banned for 6? months and have to have a letter of credit from a bank to bid again.
-Have enough staff on hand to handle issues. If I need to call about a technical issue, it is your responsbility to have someone to deal with it.
-Don't have simple technical issues, especially if you are charging to watch an auction. Numerous people have complained about not being able to see the auction.