It really depends, using me as an example. I am very introverted, and don't have the greatest social skills irl so for me to be as confident and articulate as I am online, that would be somewhat of a challenge. But over all people who express themselves online for who they are are sharing who they want to be, but have a harder time expressing those feelings because of anxiety. Anxiety actually imprisons you. For me, when I get anxious I'm not the type that will say a lot because I'm anxious, that would be the reaction of a nervous impulse, which is slightly different. Instead I become really quiet and I don't feel as sharp as I would if the anxiety wasn't there.
For people with social anxiety I think using the world of online communication is a smart way of hooking up with someone, but I think that those feelings should be taken with special care because feelings can be fragile, and the littlest upset can change them (the way they feel for the person they have feelings for.) Just with people with social anxiety don't expect them to be as socially comfortable as they appear to be online. But that's pretty obvious.
I think that if you truly have feelings for someone, and that feeling of love is mutual and shared by the one you have feelings for, then I think that it can work, and that through time, continuing you chat over a course of time, emailing whatever means to stay in touch, it can definitely work out, and is worth investing in if that's where your heart leads you.