Wise or unwise to put ads on google blogs?

Most of google ads are waste of money and waste of time to many of us. For example, I wrote blog articles to complain about the service of SONY Vaio PCV desktop, and there were a lot of Sony Vaio ads parachuting in my blog. This is because Google's spider crawled into your blog, when you updated your blog. However, they don't know whether the key word matched article favours or goes against the ads.

Another example which is obvious to us, that is , there are a lot of blog host ads. Maybe those guys believe they offer better service than google. Atcually, it is. Just look at the google blogs, there are very few templates to choose. They all look the same, a little bit boring. Some of the blog servers have more powerful editing system and are easier for ads or marketing, photos,audio or video to be edited. Anyway, you can create a blog in these hosts to attract traffic to your blogs.