do you need to format memory sticks for your PSP?

[kenshin-dono]

I got a PSP a little while ago and had a question. Do you need to format your memory sticks for the PSP? I actually bought 2 on amazon, a sony memory stick pro duo mark 2 16gb and 4gb. The 16gb was an obvious fake and the 4gb was a not so obvious fake =P I figured Amazon would be safe but i guess not.

Im returning those and buying the 16 gb one direct from sonystyle now, and the 4gb at target or frys. But when I was on the phone with sony checking on the 4gb they mentioned your suposed to format the memory cards for the PSP. Well, the manual mentions nothing about that, and the one that came with the system works fine (and the 4gb seems to work ok too) all without being formated. Is it really necessary to format these things or do they work fine without doing so? And if you DO format them can you still put moves and games and stuff on them?

by the way the two im getting are the

MS-MT16G/ECO

and

MS-MT4G/ECO

actually i was also wondering if anyone happened to know what the difference between the MS-MT16G/ECO and the MS-MT16G is (same questino for the MT4g and ECO) They didn't seem to know when i called sony either, but it seems a lot of retailers have the regular MT4g and not the MT4g/eco. On newegg.com the ECO is cheaper for some reason.

By the way i had asked some questions regarding the psp 3000 VS the 2000 here.. i kinda wish i got a 2k. The interlacing lines are obvious to me most of the time, and the wide olor space makes some games look greenish yellow. But luckily you can change the color space to normal. Nothing to be done about the lines though =(