When Is Enough Really Enough (Or Too Much)?

Beth Kanter is contemplating some great questions for anyone raising funds for a cause on social networking sites. One of the items discussed on her blog post The Future of Learning in a Networked World: Reflections From My Session is:

"How often can you ask before people get burned out by it?"
"Would writing about what I am learning about social fundraising (as
well as hitting up people for money) would that alienate at some
point? Where’s that line?"

The following are some of my thoughts (as they relate to a blog):

• In traditional online marketing I am continually taught by experts that a person needs to be exposed to an advertisement at least 3 to 7 times before action is typically taken. If that is the case, then why do we expect to be effective by only exposing a person to one blog post asking for a charitable donation?
• Consider providing value to the reader in your blog posts beyond just asking for the donation. Educate the reader about the problem being helped by the charity. Discuss the success you are having with the online fundraising campaign. Talk about the lessons you are learning. You can even work the ask into blog posts on different but related topics. Be creative.
• Since asking for a donation for charity is usually not considered "self-serving", I don’t believe several asks would drive a person away (even if he or she has no plans to donate).
• Should you care if a person stops reading your blog for this reason? What is the purpose of your blog? If it is to have the largest number of readers then I guess you should care. If it is to attract a reader you can inspire and engage with, don’t worry about the loss. That person obviously doesn’t share your same values.
• You need to stay true to the purpose of your blog. This is the one exception to the rest of this list. It will be easier to
  ask many times if your site is focused on the topic of philanthropy or
  related to the mission of the charity you are raising funds to support. If you maintain a blog about bike repair and continue to ask for donations to support a team of doctors helping in other countries, you will probably alienate your readers pretty fast.

What do you think? How many times can a person be asked to support your cause before you alienate him or her?