"Silver users will be able access what we're considering a trial period of three hours a month, which comes with video advertising. Gold users will have unlimited ad-supported access, so they can use it 24 hours a day. There will also be a premium offering on a subscription basis from Last.fm, that will be commercial free and will also have more sophisticated personalization features, like Loved Tracks."
Last.fm's subscription prices are currently $3.00 US (€3 EU or £3 GBP) per month, so you'll have to shell out an additional $36 a year if you want to avoid the ads and have full access to their service. You'll also need a Last.fm account, in case you haven't set one up already. Luckily, that part is free.