I was playing around with Rampell Software’s DidTheyReadIt service which claims to be able to tell you for how long the recipient of a message had your message open. Their other products are various forms of spy ware, too.
I thought that DidTheyReadIt was probably a refresh trick: just keep reloading the image. However, the actual HTML is very simple (and not even valid):
test.<br /> <br /> this page has a little "web bug" in it. that's an image that loads. <br /> supposedly from that the DidTheyReadIt folks can tell me when, where,<br /> and for how long you read this email (although you have to click on<br /> "display external images" in Gmail.<br /> <br /> <br><img src="http://didtheyreadit.com/index.php/worker?code=844eea38c4f0ab9bd2220f65f4107dbe" width="1" height="1" />
I tried accessing the URL in Firefox and in lynx. Data kept coming down the pipe as long as I let it. Other people tried the same thing with the same result. DidTheyReadIt just keeps pushing data at you.
I was amazed at how stupidly they did this. On a slow link, this just about killed my bandwidth (although I was loading it in three different user-agents). Imagine if your business got a lot of mail from another business using this. That’s a lot of open connections and a lot of data clogging your pipe.
Not only that, though, imagine the poor system engineers at Rampell who will have to deal with the amount of data and the number of processes they will have to run to service every open email if they get as successful as any business hopes to be! They have really set themselves up for failure, or at least lots of bandwidth charges.