Nothing I've seen really does this today, but it seems to me a question of giving other people the appropriate level of resolution.  I don't mind giving exact location information to my family.  When I visit London (which I would perhaps do once a month) I would willingly reveal my location to a range of friends to improve chances of a spontaneous meeting, and make it easier to locate each other.

However, if I had a following like Mathew Honan, I would perhaps want to offer less resolution to my followers.  Not only for reasons of security, but also just for appropriateness: what possible benefit could a strange get from knowing that I am on the M25 motorway between junction 10 and 11?

I think appropriate levels of information is the key.  Brian, you and I rarely meet in person, so location information might be a key to allow us to coincide more (assuming we both agreed this was a benefit!).  So for example, if you and I are in different countries, then probably as much information as I need is "Brian is the the USA".  Possibly timezone, in case I wanted to call without waking you at a strange time.  If you were in the UK, it would help me to know which town you were in.  For example, if you were on a flying visit to Fordingbridge, then my commitment would need to be high indeed to make me drive there (2-3 hours) on the off-chance of a meeting; however if you were in Maidenhead or London, then chances of a meeting are greatly improved.   The resolution of "Fordingbridge" is good enough for my needs: I don't need to know if you are in the office or feeding the ducks.

On Latitude:  It seems odd to me that the Google story seems to have penetrated the mainstream media in the way that no other location story so far has.  Latitude is a nice toy, and I have it on my Nokia phone with half a dozen other location tools that offer similar functionality.  Unfortunately, like all of the other location tools, it's better left switched off unless you always carry a spare battery...