Not a shock...
They stopped supporting the little guys with a concerted move to deals with UMG and others. At that point functionality in their product dropped like a rock for the little guys and consequently a lot of people that had supported them in the early years seethed for a bit then voted with their money and went elsewhere. They offer so little now if you're an unknown artist you're almost better just making your own website using a cheap package and sharing from there rather than using SoundCloud.
Still a decent platform to share music on but others such as Hearthis.at have long since overtaken them as better platforms for sharing music with features such as higher quality and lossless streaming.
They might like to quote big numbers for listeners but not many of them will be paying subscribers since the benefits for paying are very little now.