I ban grids for abuse, IP theft and other forms of bedlam.
Kristina, it might be a good idea to maybe have a spreadsheet with the grids along with the reason these grids are banned.
Avitron - Copybot, IP theft
Aviworlds - IP theft
Misfitz - child avatars, griefing
outworldz.net* & freedns.org - Abuse, IP theft
twistedgrid.xyz - nuissance
*dreamgrid (outworldz) makes it easy for neophytes to run their own grid. Unfortunately, it has become a haven for abuse from people who have been banned from legitimate grids. I had problems from freedns too so I have blocked their subdomains.