i disagree with a lot of this. there's NOTHING WRONG WITH GETTING THE EMAIL ADDRESS. it's no big deal. you guys are interpretting it way too much and thinking "oh i will come off WEAK and she won't like me if i ask for her email, wah wah." who cares? it's not a big deal.
personally, i like getting the e-mails. it's EASIER. it's safe. it's fun. she has no risk if she gives out her e-mail. in fact, she's probably USED to having guys asking for her number, and if anything will wonder "why the hell is he asking for my email?" e-mail is better because it gives you the opportunity to FOLLOW UP afterwards. i'm not that strong in my intitial approaches with them. i still have nervous ticks i'm trying to get rid of.
if she's interested in you and she gives you her email, GREAT. she won't block you, you have nothing to worry about, and you can maintain that attraction.
if she's not interested and gives you her e-mail, GREAT. when you add her to msn/email her, you now have ANOTHER opportunity to follow up and make her think "wait a second, maybe this guy is a LOT cooler than i thought!" if she blocks you, WHO CARES. you're rejected, big deal, you had your shot, move onto the next e-mail.
spend 5-10 minutes talking to her online, get her number, and you're right where you want to be.
there's no big difference in asking for a number and asking for email. they're both ways of communication, but email is just interpreted as lower risk which makes her more willing to stay in touch with you. like i said, i'm much better at following up with email. one line which i like to use from deangelo is, "if anything else, sounds like you'll make a GREAT friend." it'll drive her nutz especially since you've started with just her e-mail.
if she's not interested, i like to simply say, "that's fine, sounds like you'll make a GREAT friend. and your first job as my new friend is to introduce me to all your hot, single girlfriends."
you will get better results, trust me.