The ads are localized. Here in Norway I tend to get an ad or two (excluding the user feedback) during a 7 hour workday.

I havent heard an actual advert for weeks. Currently it is just "<insert name here> from Spotify" telling us how cool it is.

From the sound of it they don't make enough money to cover the costs of licencing the songs from the labels... though I'm just guessing this based on the article.

They are having lots of trouble selling ad space in various territories. Though I agree that the article should have mentioned it.

In the UK, I get an ad every 10-15 songs. I want weekly ads!