Photos used on auctions, e-mail, forum posts or for that matter anywhere on the web need to be small, so the amount of room on the server that your photos will take will typically not be that much.
Auctions and forum posts that you will be posting to are short time posts, so by removing photos after 30 days keeps the amount of space used by the photos on the server from growing out of control.
All we ask is for you to not abuse it, and it will always be there for you to use it!