i'm not sure how much help this will be, but i run a gaming community forum that is decently active (50,000+ posts in first year up). i have video/archive attachments set at 20mb, pictures at 10mb, and text-based files at 5mb. i don't have much worries about storage space, as space is fairly cheap nowadays, and i don't use anywhere near my allowed bandwidth of 3000 gb/month