If you're a faithful Time Warner Cable customer, your next Slingbox purchase could be on the house. Yesterday, the provider announced that it will offer full rebates to any Wideband internet subscribers who buy the $300 set-top box, as part of a promotion due to launch sometime in September. Jeffrey A. Hirsch, TWC's executive vice president and chief marketing officer, told the New York Times that the offer is geared solely toward promoting his company's $99 Wideband service, though it's hard to ignore the move's larger symbolism -- especially in light of that