You have to keep in mind, there are just as many psychos sitting next to you at your local Kinko's as there are at the other end of your modem line. That being said, most people want to maintain some sort of security while they are doing the on-line dating thing, or at least until they have met the person. There are a variety of choices to be made here. The first step is to choose some sort of free internet email account,(not your normal ISP account) that will provide anonymity for  you. You can choose from hotmail, (which recently has made news because hackers have created HTML links which steal your login and password, but don't worry, you didn't want to date them, did you?). There is also Yahoo! Mail, excite, etc. Be sure to choose a nickname that gives you some semblance of attractiveness, but just don't go "over the top". Some examples of good names: 
Pen_N_Ink,  indianajones, cocopuffs,  some lousy names are : 2fat4u, longlasting1, mousemeat, etc. You get the idea. Most of your "security" relies on your good judgement and common sense. Donít give 'em your social security number until they tell you, "I'm ready to tell you my last name today. As the wise Hannibal Lecter said in Silence of the Lambs, "Quid pro Quo, Clarice"