There is no reason to get 4gb just for web browsing, email, photo editing, ext. I have 2gb in my c2d macbook, and I do more then the average consumer in terms of usage and apps open, and it never hangs or has any problems. 1gb should be fine unless you are using pro apps like final cut or photoshop, where then you should get the 4gb, although if you only use them occasionally, it is not worth the money.
I've even used a Macbook on 512 before, and it was fine for web browsing, email and iTunes. Only get the 4gb if you are doing pro work.