With HD becoming more and more popular, 50mb doesn't give you much to work with. Should be around 100-150mb. Vimeo is a piece of shit and takes hours to actually load up, youtube sucks, etc etc. I vote yes for bigger video size.
you should have no problem compressing a 4 minute video to under 50mb while still retaining good image quality and frame size. It's all about bit rates and the right frame size.
but, it would be nice to have another 25mb to work with, 75mb would be great.
yeah i cant stand youtube. and im glad that the standard player is gonna be flash.. like freeskier.com. flash is a good mix of good quality and fast loading! but for the time being, i use blip.tv