From the beginning of July, new and more stringent rules will be applied to 'premium' SMS services (that's the dodgy ones that advertise on TV and like to set up recurrent billing in the fine print) by the Australian Communications and Media Authority (ACMA). However, there's plenty you can do to avoid getting rorted by such services right now.
From July 1, ACMA will have new legislative powers that enable it to stop dodgy operators from continuing their services, require all providers to be registered, and require all carriers to allow the option of blocking premium services on all plans. The most welcome feature of this package will be a double opt-in provision, meaning that it will be harder to "accidentally" sign up for a subscription service, as two separate confirmations will be required.
In Lifehacker's humble view, there's not much on offer from premium SMS that you can't get better and freer online, with the possible exception of voting in TV talent shows. If you are tempted to sign up, check out ACMA's guidelines for avoiding problems. They're mostly common sense, but we have to remember that hormonally-oversurging teenagers are sometimes involved. If you're trying to work out which particular service an item on your bill comes from, check out previously mentioned 19 SMS.