These numbers are interesting if you're waiting for a car or wondering if the CA rebates are going to hold out but they're not useful for much else. Bloggers writing that "Volt outsells Leaf" or posters here writing that "this proves the Volt will fail" need to put down their crack pipes.
Sales are low because production has been slow, and production has been slow because the many new components and features are forcing both companies to do extra QC in order to ensure there aren't any huge problems. Lots of buyers for the cars. Because the roll out has been through dealers, you can find a stray Volt now and again, maybe even at MSRP, and no doubt the same will happens as a few Leafs end up orphaned (if for no reason other than at this rate some people will die before their car shows up), but the entire run of both cars will end up sold. The only non-technical problem GM is having with the Volt. Nissan will have will only have similar non-technical issues, not issues with selling the limited number of cars it can produce.
If gas prices keep rising we may see even more of a supply crunch than we're seeing already.
Once production gets rolling in 2014 or so the Volt will outsell the Leaf because GM will be able to sell it more places. After this winter it's pretty clear that the real world EV range in winter for colder climates is about 1/2 what you'll get in places like SoCal during almost any season. The limited range means that at this point EVs are niche vehicles. That's not really a big deal since most truly new products are most successful when they start out will a niche and then move more into the mainstream.