I really would not recommend using a flash drive as a swap drive/virtual memory. Talking from an experience point, I had hardware failures on two of my flash drives (both Transcend make). A year ago, I used to watch movies stored on the drive and it stopped working. A few weeks ago, my friend did the same thing with my 4gb drive, and it conked off too. I guess that prolonged continuous read cycles were not a good thing. Luckily, in both cases, the drives were under warranty.
But, this is just my experience. I would like to know the views of others too.