yes, you can... Mote hooks up to USB. However, as @Mr_A pointed out, if the power draw of the whole thing outweighs your PSU, you will run into trouble.
I guess the Mote has the advantage that if you hit a wall it is specifically designed to be powered independently, if needs be. It's also modular - up to 4x 16 pixels sticks.
On the flip side, a blinkt will draw less, not least because we're comparing 8 pixels to 16 (minimum) in the case of Mote (although technically you could cut a Mote stick to any length if you really wanted to).
note that blinkt! hooks itself up to the Pi GPIO, so if you were looking at further GPIO based add-ons, this could also turn out not to be such a good idea, although that will be by far the cheapest option (£5 vs min £22).
If I were you I probably would go with the Blinkt in the first instance to test the water, but the installation will be a bit more fiddly.