Why would it be a problem to marry someone you met online assuming you check them out before you go out with them? I think it sounds better than meeting someone at a singles’ event which is very mekubal nowadays for older singles.
When people meet at a singles’ event, they are more likely to notice and be focused on the superficial aspects of other people (their appearance), but online, you can’t even see the other person, and what you notice about them is they way they relate to other people and their opinions, hashkafas and values (as well as other crucial things such as their spelling, grammar and vocabulary 🙂 )