I just finished the awesome guide on meteortips.com, but one thing left me a bit puzzled.
In one of his chapters, David says we need to use Meteor.userId() on the client side, and on the server side this.userId. However, in the next chapter he uses himself Meteor.userId() on the server. I tried it and it works.
Which leads me to the question:
What exactly is the difference between the two, and when should they be used?