It never ceases to amaze me how little people value their given name at. It appears as mentioned the reported sale he made was just $3000, apparently the name Steve Bloedow is only worth $2,000.
Networks.ca $3,000 May 11 Sedo
Very sad.
I think you have a valid claim against both sedo and the seller, absolutely. The question now becomes is it worth the legal costs involved as it will likely end up being a matter of principle.
A possible explanation of Sedo's behaviour is that they ended up netting a higher commission on a $3,000 sale than they would have on a $1,000 sale. However, this is a difference of just $200. They must be really hard up for money if this is the case, though I doubt this is the story.
JP, legal action is a very viable thing, as Ontario's small claims court allows for claims up to and including $25,000.
Not that I'm providing legal advice, as I am not a lawyer, but what I would do if I was in Wayne's position is I would threaten legal action against Sedo for turning around and selling the domain, despite using the seller's negligence as the cause for the transaction to be incomplete. The hard part here is quantifying the damages.
I would only threaten legal action, as it would be of great expense for them to come to Ontario and fight the case, whereas settling out of court is done privately and at no expense besides that of the settlement. It's not worth it for them.
However, if you really want the name, going after Sedo would be barking up the wrong tree, as it is out of their control. Where to go from here is really a matter of what you're after; money, or networks.ca.