I haven't had any issue with this site with pop-ups or spam, since September 2006, when we were spammed back to the stone age !!!
I went through our membership about a year ago when I had nothing to do a work one day, I came up with at best 35% active members .
My criteria, was logging on and making a posting within the last 6 months .
If you tightened up the requirement to 90 days, it dropped to the low to mid 20 percent range .