meet应该指真实中的见面或某种形式的相遇，比如i met her on the internet.(我跟她是在网上认识的。）而see在网络或电视等媒体见面或见到可以用，比如说i will see u on the skype.(我们在skype上再聊吧。）

Both are correct but mostly it depends on scenerio or circumstance .For example here you're talking about Facebook (technology based contact) The most appropriate words are 1- to have chat with 2- to get intouch To see is the most appropriate word when someone says : 1- You got high fever , you need to see a doctor right away . 2- Long time, no see (it's a popular phrase) 3- Technically ,when we meet people physically we could say : Where have you been , I haven't seen you for long . But for facebook we could say : That's a lot! How many of those do you actually get intouch with on regular basis ? That's a lot! How many of those do you actually chat with on regular basis ?

So I would use the first version of that sentence- "That's a lot of people. How many of these people do you actually see on a regular basis?" But you can use the other version, too. In this case "meet" can mean "meet with", like: I meet with her once a week. (get together, have a meeting, have an appointment, a set time) In your first sentence ("I had up to 900 friends on Facebook, including some people that I only met once and never saw again."), "met" means the first time you saw someone and learned their name, and so on. This is the most common use of to meet, but you can use it to mean seeing someone at a set time as well. Does that make sense?