Networking events are clearly a great way to meet people from within their target market.
This requires clarity about what your target market is and frankly it also requires anough structure behind you and the business to be able to sell on the spot - to be able to clearly communicate your value proposition to anyone within your target market and being able to more or less sell to them on the spot.
This is most appropriate for service businesses. There are also product based businesses that this applies for but those events will be very targeted, so make sure you're not just chewing up your time trying to sell to the wrong people. I suspect that social networking / digital networking is the primary way to go due to it's immense scale and somewhat lower barrier to entry with regards to the trust required.
One thing to remember here is to balance your time spent talking with any person vs moving around and finding the right target market people. Ideally you have a very very clear idea of your target market so you can find them and hunt them down within the pack because you can sense them from a mile away this is critical.