It's worth noting that the original base price was actually 87500 or 87900 (I forget which) to get that "$80k after tax credit" price point. The tax credit still applies, so the new price point is still (theoretically) under 100k, except of course one has to add state tax, tags, fees, etc., all of which generally eat the entire Federal tax credit and more.
Another theory on the reason for the price increase is to get pre-order people to "s--t or get off the pot" as the saying goes. Original pre-orders required only a $1k deposit. Orders now require $5k up front. Presumably converting an original pre-order to a "firm" order requires forking over $4k (which doesn't mean that much in the end, but every little bit helps), and failing to convert allows them to deliver the car to someone who did.
I think that the price increase may have to do with poor sales. Yeah, that may sound strange, but I'm "guessing" that the sales target / profit won't be able to be reached under current pricing structure / sales target, thus, increasing price to cover that. Potential buyers, like Eric has suggested, won't be swayed because that's just chum change in their pocket, so on paper (for FK's accounting), it'll look "good" on the financial reports.