Are Speculators Unwelcome in Multi-object Auctions?

I consider a uniform-price auction under complete information. The possibility of resale attracts speculators who have no use value for the objects on sale. A high-value bidder may strictly prefer to let a speculator win some of the objects and then buy in the resale market, in order to keep the auction price low. Although resale induces entry by speculators and therefore increases the number of competitors, high-value bidders' incentives to "reduce demand" are also affected. Allowing resale to attract speculators reduces the seller's revenue when bidders' valuations are dispersed. Speculators increase the seller's revenue only when they are outbid. (JEL D44, D83)