It's not really about accessibility, it's about the way people go about finding information. There are workarounds and there are dumb people. I've had people check in to professional athlete's houses on facebook, I've had people give out phone numbers on facebook, mailing addresses on instagram, mailing addresses on facebook (On public facebooks). It also only takes one link to end up in someone's album in someone's facebook like six degrees of Kevin Bacon style.
And as a last resort, there's also legitimate hacking.
Was it absolutely inappropriate for the girls to crash a wedding to meet the band? Of course.
Is it absolutely inappropriate for someone to post her tumblr url? Nope! It's public y'all.