Many devices have that included as a 'sig' for things like email - but there's nothing to stop you deleting it.

Personally, I quite like it. It tells me whether people tweeting (for example) are at home or away from the house, or even if they've got a new phone. But then, I'm nosy.

I'm not sure what sort of phone/device I use is in quite the same category as what underwear I'm wearing (white).