I was thinking about the benefit of uploading files with flash form can reduce bandwidth than using HTML file upload tag. Because upload files with flash form may have risk about the users which don't have flash player. Anyhow, I can say that uploading flash form is more faster than others like ajaxupload, java applet and so on. In this function, we can dynamically check the size of uploaded file and file type as soon as users browse. And, we can show dynamically uploading progress to user how much his/her file is being uploaded on our server. I can say uploading file with flash form have less risk than using html form upload tag.

Big Credit to : http://www.asfusion.com/blog/entry/file-upload-with-coldfusion-flash-forms