Even those would be hard pressed to handle 24/7/365 use as an NVR. The first big problem being the processors are not really capable of handling multiple video streams at 2Mp rates. Then there's the major problem of storage. I know, use a USB drive. Not really very useful when it comes to very heavy write operations for extended time and way too slow, even USB3. NAS is another alternative but gets a little pricey when compared to internal SATA drives, plus the network connection on the craptop would start to bottleneck with all the inbound and outbound traffic.
Blue Iris, video surveillance software, is actually optimized to run on i5 or i7, generation 5 or better, using the onboard, Intel, video processing. I can't use that processing on mine, unfortunately, but with the raw horsepower I have Blue Iris is only using about 20% of the CPU time to handle nine cameras. Those that have tried laptops have found that 100% CPU utilization with six cameras is the norm, and lags, jerky video, system lockups/BSODs become a problem. If I set up a machine that was solely for Blue Iris I could probably get away with 75-100 watts, it's folding@home that uses the most power.
I do use a craptop most of the time for "casual" computer use, but that desktop is built to handle a load, 24/7/365, that no present day laptop that costs less than $5K, or more, can remotely keep up with. Plus, having a big, flat screen, display on the desktop attached to a pretty high end graphics card makes viewing security footage really nice. Actually, I could plug in a total of ten HD monitors if I really needed to, just can't figure out why I'd need to.