I was recently at the DMA show in San Diego. During the show, I had three different people come up to me had (roughly) the same conversation with each of them -
"Why did you stop publishing your blog?"
"I haven't stopped publishing my blog"
"I didn't get an email to let me know"
"In the last email I sent, I told you I didn't want to spam anyone by sending an email every time"
"Oh. But why didn't you send an email?"
While I would love to think that people are just waiting for my new blog posts, it pointed out a much larger issue - I had made the "spam" decision for them. It turns out that my personal definition of spam was much, much tighter than what these people (which is an admittedly small sample size) were willing to bear. While I was very proud of myself for being so anti-spam, I actually did a disservice to people who would like to see my content.
When I pressed a bit further and let people know they could either bookmark the blog or subscribe to it, the response was "oh...I'm kinda busy - I like to read your stuff but I don't have the time to go searching for it." When I told them I posted on both FB and Twitter, they gave me that "I'm a REALLY busy person who has no time for that nonsense" look.
Here is the value of email in a nutshell - it's a reminder service that prompts people into taking action that they WANT to take. Due to the persistence of the email message, people can look at the reminder when THEY choose to. People need reminders. They WANT reminders. My (artificially) telling them that they were not going to get reminders took away something that they like (although not so much that they subscribed or posted or anything - it's a very slim commitment.)
This frequency argument goes on all the time in the email industry. There is a very vocal sect in the email space that claims if an email is not "pitch perfect," it must be spam. Since spam is inherently evil, then all spam must be stopped - damned what the consumer actually thinks. It's an idea that is not based on the voice of the customer, but instead on the (usually) misguided thoughts of a "marketing genius" who is more focused on their own head rather than that of the consumer.
Now before anyone gets on the "Bob's a spammer so he must be evil soapbox," understand that I'm not talking about email that - at some point - you just didn't ask for. But by artificially limiting what you send to people based upon YOUR beliefs - rather than those of your customers - you end up limiting the incredible value of your email program.
Give your customers some credit - they will tell you when they have had enough.