ok, I'll be that troll. ;)
ScanAlert's service is more of a marketing tool for specific types of merchants, and can be quite a successful one based on your customer demographics. The "Hacker Safe" logo is recognized on many larger ecommerce stores, so your average internet shopper is familiar with the logo.
Now, before I get flamed, hackersafe does not work for a lot of sites. But, if your ecommerce store attracts a lot of internet buyers who are not familiar with your business, having seals that a customer may recognize and shows your commitment to security and safety can help close a sale.
We have a number of merchants who have seen an increase in sales directly attributed to the hackersafe seal. We also have many who have not. If your store is known by repeat buyers, the seal does little to help the bottom line.
Additionally, the scanning done by ScanAlert can help find potential vulnerabilities, and can give peace of mind to a merchant that the server they host on is at least, on the surface, free from major security flaws that are publically identifiable.
Of course there are less costly services, but brand recognition when selling online can go a long way to sway a potential buyer who is not familiar with a site. In a forum such as this with extremely technical members, of course they "see through" the hype of the seal. But your average consumer online often finds solace in seeing something recognizable when wanting to purchase from a smaller "unknown" online store.