The one that confuses me is "the straw that broke the camel's back". I mean, chances are that a load that heavy would've slid off the camel's back to the side. It at least would've broken the camel's legs. And, if the load on that camel is so heavy that it has 4 broken legs, motionless on the ground, waiting for a straw to break its back, then, there are several problems. The load is useless on the back of the camel as there is no way that the camel can move it. If there is that little difference between the breaking of the camel's back, then who cares about the straw, the camel probably would've broken it himself. If there is that much weight on the camel's back, chances are that his ribs and internal organs are crushed, and he is already dead, meaning that the straw is just superfluous. That one is just stupid in my opinion.
Also, supporting camel cruelty is wrong.

Who loads a camel when the camel's standing up? Any idea how tall those fuckers are?

It basically means that you can only eat a cake once because once you've eaten it it will be gone.  Still kinda silly, but it's supposed to be a metaphor.  Supposedly, it's more poetic than saying, "if you spend your money on junk today, you won't have it to pay your phone bill next week."

It's a terrible metaphor really. The whole purpose of cake is to eat (or, as Nathan points out, to decorate). I imagine an ornamental cake would start to smell bad after a couple of months.

Poetics are fine, but some grounding in reality would be nice, like your junk analogy.

It's like putting food on credit. The bill comes a month later, but you already shat it out weeks ago.

Best analogy.

i'll see myself out.