Spotify is the last 32-bit app on my Mac.
That means when it's launched (which is all the time), OS X has to load all the system frameworks into memory a second time, but now the 32-bit versions of them, next to the 64-bit versions already there. Just to accommodate Spotify. (source: https://developer.apple.com/library/mac/documentation/Darwin/Conceptual/64bitPorting/indications/ind...)
As such, Spotify invisibly takes up way more memory than what it actually needs to run.
I can understand the need for Spotify to be backwards compatible with 5+ years old Mac hardware in use as media players and such, but that can be accommodated with a fat binary, including both 32-bit and 64-bit code.
In 2013, it is a bit strange that lots of Mac users of Spotify have to pay this memory burden of the past, while where is an elegant solution available in the form of fat binaries.
Another thread about this subject:
Hello everyone. Staff here. We’re happy to announce that Spotify for Mac is now available in 64-bit. While we don’t have any news about the Windows app, we’ll be sure to update the community once we do. Enjoy!