Book of Genesis Theme of Lies and Deceit

That sneaky little serpent isn't the only one lying in Genesis. Pretty much all of the patriarchs in this book know how to tell a good fib. And usually, their lies pay off. Does God want them to lie? Is lying is just a means to an end? And wait a second—isn't "thou shalt not lie" (kind of) one of the Ten Commandments? How do we reconcile all of this?

1. Do any of the women in the text lie? Do their lies have different motivations than the men's?
2. Are any these lies just there spice things up? You know, to get a good laugh? Is there kind of a pleasure or joy in hearing about someone's clever ruse?
3. When does deceit further God's plans? Oh, and is this cool?
4. Does the text go so far as to valorize lying?