Just as a bit of general background for this thread:
The Craig Newmark banner is currently running at 20% on the English Wikipedia. It's a pilot to see how our audience responds to endorsements and testimonials by third parties. (So far, it is doing reasonably well, but not fantastically so; we will likely move on to different messages soon.) We're not running a large endorsement campaign this year, but we wanted to at least get some data on a banner of this type to help us determine whether we want to run more such messages in the future.
We approached Craig and asked him whether he would help us with this, and he generously agreed. We chose Craig because he represents, to many people, a philosophy of the web that is comparable to ours. In spite of huge web traffic, Craigslist is run with a staff of 32 and carries no ads, and Craig founded a non-profit organization, the Craigslist Foundation, to support other non-profits. (CraigsList itself is a for-profit.) We're pleased that Craig has joined our Advisory Board, and we're happy he agreed to this endorsement. That said, any kind of personal endorsement can certainly polarize.
If, in future, we decide to run more such endorsements, we'll likely want to come up with a rich mix of different kinds of people with very different backgrounds, both to appeal to different segments of our audience, and to get a better understanding of the overall trends.