Subprime slowing holiday e-commerce?

ComScore reports that October 2007 retail e-commerce increased 19 percent over the same month in 2006. Sounds healthy, until you look at the year-to-date numbers through September, which had 2007 on track for 21 percent growth. October sales are usually a leading indicator for how e-commerce fares during the holidays, so the slowing growth rate isn't good. What's the cause? The usual suspects: increasing mortgages and gas prices coupled with a decline in housing values. Just so long as I get my iPhone for Christmas, whatevs. Here's the gory chart if you're that kind of masochist.