Must admit, I don't like the term when it's used by a total stranger towards a third party, particularly in a situation where 'sir' or 'madam' would be more appropriate. One of WCMnr's working acquaintances, the first time he met me, referred to me as 'sweetheart'. Patronising t**t. As I am old enough to be his mother, he got my evil eye/middle-aged matron of the parish voice and was loudly informed that "Mrs Simmons" was the appropriate term as I certainly wasn't his sweetheart and he was most certainly not mine.