I think there are a lot of questions there.
To specifically look at this company, it seems that they have responded in an extremely poor (out of order) way to previous suicides. And I'm guessing if there have been suicides then bullying is not uncommon on the site.
Advertisers withdrawing is what will hurt them most.
I agree that parents can't and shouldn't be aware of everything their children are up to. Teenagers should have a certain amount of freedom, as they have always done.
I think the idea of regulating the internet is technically tricky.
I wonder if, for sites aimed at young people, they should have to provide more info. Like, I don't know. Parental sign-off, a passport or ID number, something linking them to their posts? I don't think that, knowing how children are, aiming a site at them and then providing anonimity is entirely sensible. Suicides as a result of actions on sites aimed at teens are quite prevalent, more so than adults. So I think maybe sites aimed at whatever it is, 14-22 or whatever, need to have different rules in the sign-up and more moderation.