I don't have any online friends

There are some advantages and disadvantages 

Advantages:

• They can be anywhere in the world.
• You don't have to be in the same room, let alone the same country as each other.
• You don't have to smell, see, hear them if you don't want to (which is especially good in the case of smelly feet etc)
• They can be any age, race, sex, size, appearance and it just doesn't matter with a computer in between you (who cares if the person you are chatting with has hair growing out of their nose? It just won't affect you!)
• You often get closer emotionally to online friends because email encourages you to say what you really feel, think etc.
• It is easy to end the conversation when you have had enough (fake a power cut if you have to, or Oh, Look... MSN went down, I can't sign in, weird huh?)

Disadvantages:

• You can't be close to them physically, you can't hug/hold hands etc
• You can't go out for a drink, swim, pub crawl, game, etc with them easily or spontaneously
• You don't really know for sure they are who they say they are (They could have hair growing out of their nose for all you know!! see above)
• You can find some pretty strange people online (hmm)
• It can be frustrating to communicate without body language to help put things into context (Was that sarcasm, or did she really mean she is "sure I am lovely?!")
• Safety always has to be a consideration, not knowing who someone is can be fun, but there is always a chance you are talking to your local Ax Murderer)
• It is too easy to feel like you are 'falling in love' with someone online (while that feeling can be fun, it is not particularly healthy!)