Do you prefer to search for information online with Google or Yahoo? What about bargain shopping — do you go to Amazon or eBay? Many of us make these kinds of decisions several times a day, based on who knows what — maybe you don’t like bidding, or maybe Google’s clean white search page suits you better than Yahoo’s colorful clutter. But the nation’s largest telephone companies have a new business plan, and if it comes to pass you may one day discover that Yahoo suddenly responds much faster to your inquiries, overriding your affinity for Google. Or that Amazon’s Web site seems sluggish compared with eBay’s.