I am building a large website where members will be allowed to upload content (images, videos) up to 20MB of size (maybe a little less like 15MB, we haven\'t settled on a fi
The big advantage of HTTP is that it goes over firewalls and it's very easy to encrypt---just use HTTPS on port 443 instead of HTTP on port 80. Both go through proxies and firewalls. And these days it's pretty easy to upload a 20MB files over HTTP/HTTPS using a POST.
The problem with HTTP is that it is not restartable for uploads. If you get 80% of the file sent and then there is a failure, you will need to restart at the beginning. That's why vendors are increasingly using flash-based, java-based or javascript-based uploaders and downloaders. These systems can see how much of the file has been sent, send a MAC to make sure that it has arrived properly, and resend the parts that are missing.
A MAC is more important than you might think. TCP checksums are only 32 bits, so there is a 1-in-4-billion chance of an error not being detected. That potentially happens a lot with today's internet.