One can of worms.. coming up!
This is one of those highly subjective things. I personally like to find out as much as I can about the likely audience (this is more relevent for delivered products like CDs and e-mail projects) and then use that information to set my benchmark On the web you have a substantially wider possible audience and the final decision as to the cut off point is often lower (in my opinion). I just think if you are going to set standards that may exclude some viewers you need to make it REALLY clear from the outset what that level is.
That's my 2 cents.