Badger's just very good at pushing TG to its limits, with lots and lots of high-poly objects, high-resolution textures, etc. We get scenes from users to investigate support issues fairly regularly, and his are probably the only ones that have stressed my fairly capable i7 workstation (4.6Ghz, 16GB of RAM).
For most people I'd say 16GB is a good target, more is always better, but 16GB ought to meet the needs of the majority of users in my experience.
- Oshyan