In documents, it seems that there's a general tendency for labels to be emphasized more than the data that they label. For example browsers may render TH elements as bold but TD as regular weight. And in forms, I usually see the LABEL elements in bold but the INPUT elements or any other relevant data to be unbold.
In a way it seems natural - just like headings are usually in bold because they allow us to quickly scan the page and break it into chunks.
On the other hand, you might say that in most cases the data itself is more important than the label, and so should be higher up the visual hierarchy. I'm sure it depends on the individual circumstance, but I find myself tending towards making the data (in tables etc) more immediately visible than the labels.
Anyone else have any views, or know of any research on this?