The reason i disabled it is becauce attached images use RD bandwith whereas linked images use another sites bandwith (usually some image service site).
Actually most of the people here who post pictures don't use image service sites. They just hotlink the pictures directly from the original source and steal the bandwidth of those sites.
There are many image service sites specifically geared towards hosting pictures that people could be using instead of taking the bandwidth of the original sites. TinyPic.com, Imageshack.us, Imagetitan.com, and Photobucket.com are some of the sites that I use on a regular basis to upload and post pictures at other forums as most of them don't allow hotlinking at all. If you're posting the pictures directly from other sites (zimbio, daylife, getty, cotilleando, etc.), then you're hotlinking. It takes a little more time to post pictures when you save the pictures and upload them to dedicated picture servers, but it's the right way. Hotlinking is theft, period. What Is Hotlinking And Why Is It Bad?