People with a need
Saying machineguns are illegal is like saying explosives are illegal then watching demolition crews blow down buildings.
Nothing is illegal if you have the legal permits to have them.
As for Youtube videos
LE depts. issue them to officers, LE dealers have them to sell to LE depts., there are plenty of guns made before 1986, security firms for nuclear plants have them, not all Youtube videos are from this country, not all countries control machineguns,
How do you think Hollywood makes movies with machineguns, it's about money and permits and taxes.
There are rental places all over the country where if you don't have the money to buy you can shoot a gun and make all the youtube videos you want.
Here is one.
http://www.machineguntours.com/site...ntType/ViewType/PropertyTypeID/5/Default.aspx
Las Vegas has at least 3 places renting machineguns to Japaneese Tourists.