Apple (Nasdaq: AAPL) is in store for a busy weekend starting today.

The iPhone 4S launched at 8 a.m. local time around the world, from Japan to the U.K., and is being welcomed by hoards of people who set up camp as early as last night just to get their anxious hands on the latest and greatest iPhone (but didn't have the premonition to preorder a week ago). The annual event, although delayed this year, has become a pure media spectacle, and some attendees must simply enjoy participating.

Apple co-founder Steve Wozniak was first in line at the Los Gatos, California, Apple Store, setting up a chair to kill time on his iPad and put on an all-around show for fans seeking pictures and autographs. It's hard to imagine he didn't have the foresight to preorder, since he also stuck it out the old-fashioned way last year.

Demand for this year's model is unprecedented, with preorders topping a million in one day among domestic carriers AT&T (NYSE: T), Verizon (NYSE: VZ), and Sprint (NYSE: S). Shipping times for new orders placed at the Apple Online Store have slipped to 1-2 weeks, and Apple has reportedly kicked up its orders to meet demand.

Estimates for this weekend's final tally are as high as 4 million units, more than double the record 1.7 million units moved last year. Apple will shatter that record this year, but by how much? Last year's iPhone 4 launch only featured one carrier, AT&T, before its coveted exclusivity ended earlier this year.

While Apple's own retail stores will carry the most inventory for walk-ins, the company has continued to expand distribution through retail partners. Best Buy (NYSE: BBY), Target (NYSE: TGT), and Wal-Mart (NYSE: WMT) will all be selling the device, as will the wireless carriers' retail stores. Desperate buyers who aren't willing to sacrifice their day waiting in line will have to try their luck on eBay or Craigslist.

When has a Google Android device launch ever drawn this much attention?

What do you think? How many iPhone 4S units will Apple sell this weekend? Are you buying one? Are you waiting in line right now reading this? Share your thoughts in the comments box below.

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