Video editing is a big part of my job, so I highly recommend you build a system that fits the type of content you'll be exporting. My editing rig is an overclocked 3770k and 8 GB of DDR3 RAM, with a 660 Ti so I can play games. I've never had any problems with it and the longest thing I've ever edited was a half-hour episode for a TV show. I don't push beyond 1080p, and I haven't experienced any bottlenecks with the amount of memory I have, although I do plan to upgrade when time proves it necessary.
If all you're doing is making videos for the web, then any modest gaming machine will do the job just fine. If you want a better example of how extreme these things can go and how much horsepower you actually need to get a job done, watch this video: