It's a borderline call. Adding a forum is always a compromise between differentiating different types of threads or contributing to "forum bloat", the tendency for the number of forums to continually increase. The iPad forum gets about 22% more activity than the iPod touch forum, and the iPhone forum overshadows them both (the percentages could changer over time). At some point the number of iPod touch help threads might be worth yet another forum. Right now there isn't a huge volume of iPod touch threads. More than a week's active threads are typically on the first or second forum page, not buried and pushed out of sight as a help thread in the main iPhone forum might soon be.