I keep hearing that 80g is the going rate for a 5 gallon brew. That's 40 pints so 2g a pint. A teaspoon is nominally 5g so that's a smidge under 1/2 tsp per pint which all sounds about right.
Unless, like me, you like a few more bubbles... I'm going to 3/4 for my ales and at full tsp for my lagers and pilsners now...
...I chucked a good 100g of treacle in my Stout and, to my palette at least, it made a world of difference. Just that extra little bit of fizz gets a better head on the pour and a zingier mouth feel.
YMMV.