Do activity stream entries get deleted when app is uninstalled?

To my knowledge they shouldn't because they are actual entries in the Activity Engine tables.  The only thing I can think of is that there may be a sweeper thread that does some maintenance on that table that may check for valid references, but again, that is just a guess.  I will ask internally to see if there is such a process and see if I can get some clarity as to why the old user's were blocked out. 

I vaguely remember the details, but could you confirm if you were using Jive Connects at all?  Also, is this an App via Dev Console ... or an App deployed with-in an Add-On?