I just finished reading an article in which the writer gave some (in my opinion) poor information and even poorer recommendations about memory for laptops. I am not a hamster or a technician but I do know enough to spot poor advice when I see it. They started out with what I have to say is probably an explanation that caused more confusion than it answered. i.e. those knowledgeable enough to pick out the accurate parts of the explanation don't need it and those who do need it will probably never figure out the parts they need to know if that article is their only resource.
The truth of the matter is that laptop memory isn't really much different from desktop memory except that it's in a smaller package because laptops generally don't have a whole lot of room inside.
One of the things I think that the writer got wrong was recommendations for how much memory to get. They suggested that 512mb would be plenty for playing games, making videos or creating DVDs. I guess if your game of choice is one of those that comes with windows or is four or five years old then that recommendation will do. If you want to play anything written in the last couple of yeas, odds are good that you'll be better off with a LOT more than a measly 512mb.
Having spent a good deal of time playing around at making videos in the last year (and even publishing a few) I can tell you that when it comes to processing video, you're going to need more than 512mb. Especially if you're doing a lot of effects or making high definition video.
Another thing they said was that if you're going to be using vista, you'd need 1gb. yeah. right. I've read enough about vista and had some experience with it myself to say that if you're going to run vista you should consider 2gb to be a minimum and get more if your computer will support it.
The long and short of it is that, in my experience, there is no such thing as "enough memory". The only acceptable solution for memory is to always get the maximum capacity that your CPU & Motherboard can address. If you get less than that, sooner or later you'll end up shopping for upgrades. That goes equally for desktops and laptops.
My desktop machine has 2gb of ram which is the max it can handle. If it could take more, I'd want to double the ram, or triple it.