I would remind you that this is a free site, because it is advertising-supported.
This is the advertising arms race. First we[*] had some relatively unobtrusive banner ads, then they started flashing and distracting us, then we got pop up/under ads. When the adverts are irritating people more than selling to them, it's not a good thing because either people pointedly ignore them, or look at them enough to see whose ad it is so they can avoid the company in the future.
It's interesting to note that Adblock Plus acquired an "allow unobtrusive adverts" option, presumably in an attempt to get advertisers to behave and halt the arms race. I suspect it was becoming popular enough that some in the ad industry saw that compromise was needed.
It comes down to the fact that if you allow adverts that annoy and distract me, and in some cases eat up my CPU bandwidth for no good reason, don't be surprised if I take measures to block them. It's also not unknown for ad servers to deliver malware courtesy of scripts, so if it's not a static image then some other part of my browser security is likely to take it out to avoid that happening. Flash-based ads are another level of evil (also see bandwidth comment) given the holes in Flash and the Flash cookies that get set and can be used for tracking.
This site already tracks outbound clicks via viglink, and there's the mysterious ibpxl.com, the name of which gives the impression of being there for tracking purposes. The ibsrv.net site appears to host the scripts needed for the forum to work, then there's scorecardresearch and doubleclick for general tracking and adverts. It's interesting that you don't seem to have succumbed to Google analytics, at least not on this page.
[*] The general 'we', not picking on any particular website here.