Quoted from FlippinJB:
Just to add to the grammar mix, a comma before a coordinating conjunction is perfectly fine if it aids the readability of the text - especially when the conjunction is coordinating longer independent clauses. It allows the reader to take a 'mental breath'.
I don't know whether to buy a Wonka or wait for deeproot to come out with something. I have a blank space in my line-up, and some cash in my pinball pot (a bit goes in from my wages each month!) Hmm. I just wish they'd say *something* more than they have so far!
Commas are required with coordinating conjunctions, no exceptions, but if you read the quoted sentence, the conjunction is not coordinating. A coordination conjunction (and, but, or, for, nor, yet, so) requires indpenendent clauses on either side; otherwise, the conjunction is just a conjunction and does require a comma. Commas with conjunctions that are not coordinating happen often, and in the case provided, one could be used. I just wouldn't use one, and it's definitely not required.