People realizing that bitcoin cannot crash and die like a stock, and after seeing it's recovery from the last bubble, I think they're doing some real homework and realizing it's potential.
The word is spreading and demand is going up, but half of the Bitcoins that will ever exist have already been distributed, and after the block split, there are fewer new coins going up for sale.
You can't forge them and they can't be seized. You can encrypt and backup your wallet, then bury it/email it/print it, and the coins will still be on it regardless of where you accessing it from.
Bitcoin is beginning to click