The episode in question finished 3rd (of 4) in the 18-49 demo and 4th (of 4) in Total Viewers so I'd say they could use some attention. I think a lot of people gave up on the Simpsons around Season 10 and have never bothered to look back.
But just because you saw this on Hulu or Youtube, does that mean you'll go back to watching The Simpsons? Awareness marketing doesn't help The Simpsons because everyone's already aware of it. And this doesn't accomplish much more than that. If anything, it's awareness marketing for Banksy.
I'm not sure that's entirely true. If you think the Simpsons has become formulaic (which it had in some of those middle seasons) this might be enough to convince you they're taking risks again. Which MIGHT get you to tune in.
I'm not saying it's super effective but it's positive attention and that's worth something.
Source: http://tvbythenumbers.com/2010/10/11/tv-ratings-against-sund...