Overbidding on junk auctions of poor-condition Wheat cents or gold-plated State quarter collections wastes funds you could use for pursuing great coins.

Proxibid charges bidders a 15% buyer's premium but is not requiring auctioneers selling coins to post a photo of those coins. Bidders will migrate elsewhere.

With 18% buyer’s fee, coins offered with "no reserves" often actually are selling close to or over retail.

Use of smartphones is increasing for numismatic bidding. Platforms too slow to adapt to the vagaries of mobile technology will suffer.

A new “best practice” is to slap a watermark on coin images to promote the auction company, without a care how that detracts from the coin's condition.

Buyer’s premiums at top auction portals push online bidders toward cheaper portals where few rules govern lot descriptions. But bid there at your own risk.