But how well do we know her; what are we writing to her about; and don't we usually dispense with the commas after "sincerely" or "faithfully" in modern business correspondence?
The comas can be left out. I'd use 'sincerely' with a name regardless of how wel I know them. If I wanted to use 'love', then I'd normally be on first names terms. ;-)
I meant 'commas'. ;-(
What's so wrong with the comma?
Dear Mrs Hasan
You are the worst employee I have ever had in my department. You are fired.
H.D. Smith (Manager)
Must be sincerely. Anything else would be too personal. If you're calling her Mrs., you woldn't sign it love.
For 50 years I have used "Sincerely yours," for all formal communication. It is a standard use in the USA. When the "Yours" is placed first, it implies a personal knowledge of the addressee.
That's different from British English, where the distinction is on whether we use a name or not, and not whether we know them or not.
faithfully is used when using Sir or Madam - love is personal
The rules of official letter writing (the Gospel according to LCCI and Pitman Board of Education):
If you open a letter with "Dear Mr/Mrs", close it with "Yours sincerely".
If you open a letter with "To Whom It May Concern", close it with "Yours faithfully".
Mega lolz @ colyn's post - priceless. :D
Oh, for crying out loud. This is 2013. Yours faithfully/Sincerely is so old-fashioned. Just write 'Best Regards'.