Discussion on a previous thread also suggests that Fogbugz suffered the same fate due to growing slower than Atlassian: https://news.ycombinator.com/item?id=920668
On a tangent, it's kinda funny how part of the "geek" community will complain about the big players dominating and ruining competition (Microsoft, Oracle, Apple, even Linux sometimes), but on the other hand anybody who doesn't completely dominate their competition is lambasted for being a failure...
[1] http://www.actian.com/products/operational-databases/ingres/
I last used FogBugz in 2008 and it's still my favorite bug tracker. I have used JIRA extensively and while you can configure it and add addons/plugins to it to make it do your bidding, it's just not a nice off-the-shelf solution without configuration (stuff that I usually don't have the access to do, and that I get tired of asking for).
Funny how this stuff works. I wonder how Fogbugz is doing today. I do understand they must have done well with the Trello stuff.