iesnare is basically a tracking cookie. What the company that created it does, is keeps a database of specific IDs. Each PC that has iesnare installed in it's browsers gets a specific ID. This allows them to sell the information to various game companies, and other online services. Their supposed intention is to allow them to use the information to track when people make bad credit card purchases, or chargeback, so others can blacklist them. However, it's possible to be, and has been, used for other purposes. Since the tracking cookie keeps tabs of whatever you buy, whenever you buy it, they're basically assembling a database of users who spend money online. This can be used to target specific ads, events, and offers only at users who're likely to spend money. This means game developers using iesnare could decide to offer incentive events, such as cash bonuses, or cash giving events only to people they know have cashed in other games. This would mean that games could, and likely would, become even more split, with the companies able to safely ignore any user who hasn't used cash to purchase in other games, and then GP players could be entirely ignored until/unless they spend cash. This would make the free to play model even worse, as the games would literally be pointless to play, because the developers would have gained the ability to tell who they should ignore and who they shouldn't ignore.
For this reason, I'm totally against it. It's a tracking cookie, it's tracking my purchases, even if it's not saving my credit card info, it's an invasion of my privacy and should not be legally allowable. I've watched the MMO industry from near it's beginnings, and it's only sunk further down the hole as it's gone on. I'd like to see it not continue to do so with the aid of tools like these.