These types of tricks are cheap.
I put them in the same category as the "like on facebook to continue playing game."
I put them in the same category as misleading or downright hidden options that are hard to navigate and change every couple months - skip to 6:00 in the video and reset (facebook).
I put them in the same category as signing a user up for 50,000 daily alerts when you create an account somewhere.
Harry Brignull's 90 Percent of Everything covers this topic and provides a large amount of examples of these dirty tricks. If this kind of stuff interests you at all, I strong recommend this piece. Crtl+F the following quote to skip Apple's hidden settings.
The problem is, they work. The like on facebook pop ups work. The wikipedia "donate now" banner works. The subscribe to see content works. And when you have to deliver numbers to your boss and the incompetent micromanager who knows nothing about web or user experience only sees 3 new signups this week, you are required to do something.
No web developer or designer wants to include these things. Most just want to make a beautiful site that people visit. Most actually like it to be as functional and neat and have all the proper hierarchy and navigation and organization. These are the things designers jack off to every night.
But the ones managing the project - the bosses, the number crunches, the marketing team, the sales team - they don't care. We are now at a point that these pop ups are widespread enough that even the most technically incompetent boss sees them when he visits "6 Ways to Make Your Team Work Longer and Harder without Paying Them More" links. And then he prints out the page, walks it to the web design team, and says, "why aren't we doing this?"
The only way to fix this issue is to (1) make them not work as well or (2) shame them excessively until it's in bad taste to have these lightboxes.