Yes!
No!
Well, maybe!
As with anything it really depends. I don't mean that to be a cop out, but just as I can tell you about my success stories meeting everything from friends to one night stands to meaningful relationships, I can just as easily tell you about the losers I met along the way.
This, incidentally, goes for any means of meeting people… singles' nights, blind dates, the laundry mat… there are tons of ways of meeting people and in each case you are not guaranteed success.
Using the internet to meet people can be just as effective (and just as frustrating) as any other way. If anything the internet provides a safety buffer when it comes to confidentiality. You can take your time without the same pressures as when someone is standing in front of you asking for your number.
You also have a better selection. At a club, you only have a limited selection. On the internet you will likely have hundreds or thousands to choose from. It’s a lot easier to look for people with similar interests via a search form than wandering around a bar. For example, what if you liked bookbinding? Chances are most people who have that hobby are not going to be wearing t-shirts reading "Kiss me, I'm a bookbinder" (although if you see one let me know!).
Another benefit to on-line services is the opportunity to get to know much more about the people you meet. Your conversations can go on indefinitely without fear of disruptions or closing times. People are also less defensive, so are more likely to share things about themselves they might not have done in person.