How do you deal with attachments on your forum ? It could be pictures, other image formats, a zip file and so on ? Some of them can even break your forum. Not to mention the bandwidth you have to spend on it.
What is your policy on attachments ? How do you deal with it ?
Take proper precautions and allow safe and standard formats. Almost all CMS support this.
I agree that there are certain grey areas when we host our own attachments. Some might have legal complications too. But not hosting will cause even bigger issues in long run.