So the sidebar got stretched by about 30%. No problem. This entails a change to the network-provided ads (not visible above certain rep thresholds) and to the community ads. No problem. Some old ads ran with some extra whitespace while they were updated. No problem. We need to update all our community ads to the new size. Grumble, but no problem, it's a good opportunity to spiff up the graphics on some of them. The community ads thread got delayed a bit this year. Absolutely fine. We don't really know when the 2016 ads kick in. Not awesome on the lack of clarity, but not a problem as long as nothing terrible comes of it.
This is a problem, though:
This ad is currently running and it comes from the 2015 thread. For comparison, here is that advert as posted:
If you're going to run 2015 community ads in the expanded sidebar, pad them out with whitespace instead of stretching them.
Quite simple, really.
This question first posted on Meta Stack Exchange. Re-posted here as a signpost as it affects this site; give the MSE question some love if you agree with it.