I've even had them interrupting longer tracks and that really is unacceptable.
I think we all reluctantly accept ads if, for whatever reason, we either choose not to pay or just can't pay, but it's getting to the stage that Spotify are liable to lose "free" users in droves. Spotify's advertising revenue is bound to decline if they can't provide sufficient user figures to justify advertisers' further involvement.
In both users' and Spotify's own interests they need to pause and think about the impact this is having on both sides.
Has been out of control for me the past couple of weeks. At least 2 to 1 ratio of Ads to tracks. And of course it's the same handfull of obnoxious ads. I literally cannot listen to it. Time to head back to Pandora.