A hashtag is this symbol # - users of Twitter use it to reference a subject that their tweets are on. For example,
rlhere is all the Rugby League talk on Twitterrl. It's a great way of talking to like-minded people and a very natural way to increase your follower numbers, and less effort than spamming public forums.
The AUP will no doubt have a part that prohibits you from spamming the boards, that's the issue - not how to get your Twitter follower numbers up (although
rlfeel free to nudge me closer to 2,000 if you likerl
)