Against
When you 'chat' with someone you miss 2 key elements of normal 'live' communication, tone and body language. All humans communicate via verbal language, speech tone, and body language simultaneously when speaking with someone in the flesh. The body langauge and tone give subtle ways to 'read' or get to know a person which are unavailable when chatting with someone online or on the phone (which is better then online, but you still miss the visual body language). Since when 'chatting' with someone you have no 'visual cues', you are also much more likely to be deceived then when speaking with someone in the flesh ( how many absolutely gorgeous pictures of women have you seen, that in reality end up being just average looking women, or worst? How many men give the impression of wealth and success when in reality this is not the case?).
I also would like to state that the 'online dating enviorment' is skewed VERY favorably toward the female. Even 'average' looking females are given almost celebrity type attention from men online. This can be somewhat intoxicating for the females not used to being treated this way in person, and they generally have no trouble meeting a much higher quantity of men then is normally the case for them by 'conventional means'.
I would summarize by saying that although there are some advantages to meeting people online, such as being able to speak to people outside of your normal 'social circle', or people in distant and diverse parts of the country or world.......I would advise that trying to form a romantic relationship in this manner can be disastrous.
Note: I do realize people who lack the 'confidence' it takes to talk to a member of the opposite sex may find the task less 'intimidating' online, but generally I would advise that it is perferable to find a way to overcome this deficiency rather then trying to work around it.
Final thoughts: If you're male and have a confident attitude I am sure you will do better meeting women by conventional means. If you're 'very shy' about approaching a female then perhaps you can give the 'online method' a try, but do so only while exercising tremendous caution....not everything is as it may seem.