A List Of Things Thrown Five Minutes Ago

BECAUSE YOU'VE BEEN GONE: Bryan Garner, Garner's Modern Usage (Oxford University Press 1993) at 725-26, on "since":

This subordinating conjunction may bear a sense either of time or of logical connection. Despite the canard that the word properly relates only to time, the causal meaning has existed continuously in the English language for more than a thousand years.

James J. Kilpatrick, Making a Case for "Because":

Let it be conceded, up front and without a single quibble, that "since" can function as a conjunction meaning "inasmuch as" or "because." Thus, it is permissible to say, "Since we ran out of Scotch, we'll have to drink gin."

Yes, Kilpatrick prefers "because" because -- or since -- it is usually clearer and less casual (though not necessarily less causal). That doesn't mean that "since" is wrong. A capable writer is entitled to use his or her judgment.