Oh, man! I don't care how many countries they do it in. Or who endorses it. It's stupid. Referees walking around with hazardous materials like cans of spray paint in their pockets is not a good idea.
If they're going to do it, they should do it right. Marking the field is not the job of a referee, so they should have the ground crew come out and draw an arc of with a radius of exactly 10 yards. That should be enough of a crutch for referees who need a crutch. -Not to mention taking a lot of time and making the game into a joke. (but not any more of a joke than if the referee does it)
Sheesh! A referee can give a card, line or no line. (The card should be in the pocket that doesn't have the spray paint in it)
It a stupid idea, and I'm not just saying that because Ty Keough endorses it. (although that's not necessarily a bad reason)
Blue lines. Yea, right!
I'm embarrassed for the leagues in Brasil that do this, and for any leagues that are considering it, and I feel a great deal of sympathy for referees who may be asked to make fools of themselves by doing it. If I ever see it happen I'll be hard-pressed not to make fun of it.
I've survived (and made fun of) blue cards. I can survive blue lines. Anyone for red lines? A player can really get in trouble for crossing one of those!