anyone had experience with selling vacant land, using an online auction

As a experienced Auctioneer I can tell you that online Auctions only work if you have the stomach to start at a very low price and offer to the highest bidder with no further reserve.
Whwn sales are conducted on line especially by non professionals the credability factor is very low and unless properly targeted has a poor prognosis. Most qualified Auctioneers, who specialize in Real Estate work on a buyer premium [ commission added ] basis the seller pays marketing cost.Do your self a favor higher a pro or use a aggresive Realtor

The success rate is very low but if you don't need to invest anything in the process and go in with realistic expectations then it may be worth a try. It would seem that the ease of participating is attractive to buyers however my experience is that serious buyers prefer the transparency of a live open auction event. One of the drawbacks I hear from some of my peers who conduct on-line bidding for commercial property is that it is tough to generate bids which conform to their terms as opposed to an open auction where buyers must adhere to the seller's terms. Glad to discuss with you further if you like.
Jim Blanchard
jblanchard@inlandgroup.com
(630) 990-8657

I have had good luck selling land on e-bay using an opening bid amount or best offer auction style.

They are tough...
Gregory Garver - Commercial Real Estate Broker
Broker License# 01716531
(415)225-9894
gregory.garver@gmail.com