Atlantic City's most profitable gambling palace, the Borgata Hotel Casino & Spa, confirmed today that it laid off about 400 of its staff this week. The 5.5 percent cut in its workforce of about 7,600 was unavoidable in the deteriorating economy, said Rob Stillwell, a spokesman for Las Vegas-based Boyd Gaming Corp., which co-owns the Borgata with MGM Mirage. The Borgata layoffs follow Harrah's Entertainment Inc.'s announcement Friday that it was cutting hundreds of employees at its four Atlantic City casinos...