If I can't save the logo off your web page, I'm not going to include it in a blog post.
Too many web sites make it too hard — the company logo is on a complicated background or hidden in a flash animation.
Lesson: If you want people to spread word of mouth about you — make it easy. If you don't want them to use your logo — too bad. They are going to do it anyway, so at least make sure it looks good.