Previously, all things iPhone were the province of O2, which had been Apple's exclusive partner since the . (True, Carphone Warehouse also sold the iPhone in the UK, but when it came to signing up for cellular service, O2 has been the only game in town.)

PC Advisor that Orange--which claims to have the largest 3G network in the UK--will sell the phone through its stores, Web site, telesales channels, and select partners. Pricing hasn't been announced, though don't look for Orange's iPhone price to undercut what O2 offers. Carolina Milanesi, research director at Gartner, tells IDG News Service's Mikael Ricknäs that in other countries with multiple iPhone carriers, the price offered by one operator tends to reflect the price offered at the other.

Multiple carriers can benefit consumers in other ways, however. When this summer's iPhone 3.0 update brought tethering capabilities to the iPhone, Australian carrier --an apparent challenge to rival carrier Optus, which had planned to . Here in the U.S., of course, where we have just one carrier for the iPhone, iPhone 3.0's tethering capabilities aren't yet supported--and there's no indication when they might be except for AT&T's vague promise that it's coming.

For Apple, the benefits of adding another carrier in the UK are obvious--it gives the company access to new customers who didn't buy iPhones when the devices were offered only by O2. In --more on that in a moment--Piper Jaffray senior research analyst Gene Munster noted that multiple carriers help Apple achieve greater market penetration. In France, for example, Apple's market share jumped after other carriers began offering the iPhone earlier this year, . (Ironically, it was Orange that enjoyed an exclusive iPhone arrangement in France; now Bouygues Telecom and SFR both offer the iPhone to French customers.)

It's unclear how many countries in which the iPhone is available have more than one carrier--Apple didn't return a phone call requesting that information--but I count at least eight fairly large markets where there's more than one game in town: Australia, Austria, Brazil, France, India, Italy, Portugal, and Switzerland. Major markets that still retain a single carrier now that Orange and O2 are duking it in the UK include China, where , Germany, and the U.S.