I've noticed a number of businesses that operate multiple stores under different brands are using the tabbed navigation approach to switch between stores:
Avenue, Avenue Body, Cloud Walkers
The first time I saw the tabbed approach was on Gap stores: Gap, Banana Republic, Old Navy, Piperlime (and now Athleta)
Gap's innovation was to use one universal cart for all brands, for a seamless shopping experience and low flat-rate shipping. Though the tactic drew criticism from those who thought it a branding sin, Gap's president Toby Lenk explained to us at the Shop.org Summit, 2008 that the decision was customer-driven (yes, focus groups were recruited) and "the best brand strategy is to do things that customers love, not what the brand marketers think customers want."
Offering new brands like Piperlime, and now Athleta, allow Gap Inc. to use its own navigation menu as an online advertising medium. Not only do the legacy brands introduce customers to the new pureplays, but the new brands also help sell legacy brands.
Something to think about if you operate multiple stores - even if they serve different market segments or sell different types of products.