Basically .. there are many photographers who feel that photos should be exposed as much as possible without burning the highlights (checking the histogram for all colour channels on most DSLR’s) ..
The idea is not clipping while preserving as much detail as possible in the shadows where the signal/noise ratio is very low while also preserving most of the tonal details residing in the right bright illuminated part of the curve where there is a high signal/noise ratio ..
Photos will need a bit more processing in the RAW converter, especially to recover the contrast and colour intensity which usually look washed out .. and to recover the highlights up to a stop or two depending on the camera dynamic range and bit depth ..
This is of course done only using RAW and not JPEG ..
Exposure to the right of the curve (histogram) is discussed in detail at Luminous Landscape and is worthwhile considering in practice .. please read their very informative article http://www.luminous-landscape.com/tutorials/optimizing_exposure.shtml