[Marco van Herwaarden]

1. In addition to the MEDIUMTEXT datatype, there is also a LONGTEXT which can hold up to 4Gb.

2. Usergroup, forum & permission data is serialised into the datastore where all the data can be read into memory from a single read. This is a "cache" to speed up the forums.

The problem is mostly the permission, read into memory for each pageload:
- Data for all forums (name, description, settings, etc..)
- Data for all usergroups
- Permissions for each usergroup / forum combination (this can get huge if you have 1000 forums with 1000 usergroups)

Your server will probably quickly run out of memory.