I like earning points, gives me something to do and something to save up for. I also think getting free things in exchange for reviews is great too, by only getting 1, it gives you time to really write a good review, because you only have to focus on one, rather than having a bunch on your plate!
some sites don't give away free things, and EF has some great free stuff! more free is good, but I don't really think there would be a point in saving up if we got a bunch of free stuff
1 is enough for me!