Not always, just temporarily. You see, I know about the personal nodelet (see the first or second sentence of the OP :) and it's a great tool, but while I'm reading I come across many articles that I would like to vote on but will not have votes for until the next day. Instead of adding these to my personal nodelet and removing them later, it would be nice to flag the suckers for easy access as soon as I get my votes back.
I'm sure we could come up with some other uses as well. The personal nodelet seems cumbersome for something as dynamic as I'd like.