I would recommend to all AutoCAD users to run a -PURGE command, then select RegApps, * for all, and no to verify names. You may be surprised at what you will find. I briefly went over this in the PDF i posted but this needs reiterating. Regapps are added when you use certain software, and by implementing certain command. If you purge these out you will find that your drawings will open much faster. I have not experienced any problems with purging the regapps out because AutoCAD will generate these back as it needs them. With a clean drawing i have about 8 RegApps in my drawing. But i Have cleaned some that have around 157,000 RegApps. Cleaning that file, the size went from 3 MB to 400KB.
The Main thing with RegApps in a drawing is that they act almost like a virus, if you xref in or insert an "infected" drawing, the RegApps propagate into the current drawing. That is why you need to make sure when you get files from an outside source you really should clean out the RegApps. The only way to clean these out without third party software is by using the "-PURGE" command on the command line, (not through PURGE) and you need to specify RegApps. (RegApps are NOT purged under the ALL).
Thanks for reading through this, happy less file sizes, and faster loads!