I have always tried to answer this question, and somehow even after reading a lot about it, the question is still a debate in my mind. Anyhow, writing what is clear to me :
Facade layer, as the name suggests, is something beautiful which is trying to hide something ugly behind it. In spring or any other framework which uses this layer, facade serves as an interface, which is hiding some complex implementation.
Service layer on the other hand can be said as that “complex implementation” which facade layer is hiding. It connects with DAO layer and does all sort of complex stuff. It is also used to provide functionality like security etc which makes it all the more complicated.
So far so clear. Will edit if i get more.