Now that their is much more symmetry between the consumer and the marketer, I'm noticing more hesitancy on the part of marketers to act. They are in fear that too much email may infuriate someone, so we shouldn't send email. Outbound telemarketing may anger someone over dinner, so we shouldn't ever call.
My experience is that angry individuals are always in the minority, tend to be cranky in general and probably wouldn't buy from you anyway. The key to all this is to always act within brand character and consumer expectations of your brand.
It's impossible to predict exactly how often someone wants to hear from you until they respond and tell you. My guess is that like anything else it follows a bell curve with the top 20% of consumer loving your communications and the bottom 20% wanting less. In the age of 1:1 communication we can easily control for this anyway through opt outs and by just asking.