I can shrink many files down using NERO to a fraction of the original size. Certain types of editing though are best done in another format besides MP4.
Youtube uploads are converted by Youtube on their end to reduce size also.
I just noticed the last video link you posted is only a meg (roughly) Shrinking them further would be pointless. Ive uploaded huge files to Youtube. There are even complete 1hr long+ videos on Youtube.
There are even 1080p quality videos and the ability to watch them in lower quality if needed.
Such as this one