I agree with Jim, I always use the native aspect ratio (3:2 for NEX) when taking pictures, and crop later.
Another factor, is whether you're using landscape or portrait orientation. For portrait orientation, it definitively does not make sense to use your TV aspect ratio. 16:9 would be too skinny and tall. In fact, I often crop my portrait orientation pictures from 3:2 to 4:3.
On some Panasonic GH and LX cameras, there's a nice multi-aspect-ratio feature. The sensor is slightly larger, that at picture taking time, you can pick 4:3, 3:2, or 16:9, without loosing anything.
Sony NEX 5N * 2; Panasonic GH2/G3/GX1; Nikon D200/D600
SEL1855, Σ19+30; Adapted lenses in Canon FD, C/Y, Konica AR, m42, Minolta SR, Nikon F, & Tamron Adaptall mounts