Big Brother Bloomberg is watching. Smokers who've been buying cigarettes from Internet sites to beat the city's $1.50-a-pack tax are in for a shock: tax collectors know who you are and are now sending out thousands of bills going back more than two years, The Post has learned. Andrew Hoffer, a utility worker who lives in Queens, told The Post he was flabbergasted to get a threatening letter from the Finance Department demanding $1,005 for the taxes due on purchases he made back to July 2002. "I had a feeling of violation," said Hoffer, 37. "Internet purchases are traditionally...