President Barack Obama’s demand Thursday that Congress clamp down on the size of banks and their investments got major blowback from New York City Mayor Michael Bloomberg, who said it could cause layoffs and hurt the city. It’s a clash between the president and the mayor. President Obama wants to whittle away at the size of the financial services industry. “The American people will not be served by a financial system that comprises just a few massive firms,” the president said. But Mayor Bloomberg said the banks and Wall Street are part of the bedrock of the city’s economy, and efforts to slash their business just means less tax revenue for the city, which brings up the dreaded “L” word.