I tend to be less interested in gardening blogs when they stray too far from gardening, or if it looks obvious that they are pushing particular products or are overloaded with ads.

You have some ads, obviously so do others. I generally just ignore them. And so far, I've not put in ads on my blog.

In general I'm quite happy to see targeted advertising. No-one makes me click on it (99 times out of a hundred I don't) but just occasionally I see something that is exactly what I'm looking for - or even better something useful which I didn't know existed. But I would certainly lose interest very quickly in any blog that didn't stick to the topic I went there to read about.

Stuart, I've put ads on my blog as well---a few affiliate ads that are related to the topic at hand, as well as amazon ads when I talk about a particular book. They don't bother me when other bloggers use them, and I haven't had any complaints about mine yet. There is nothing wrong with trying to make a little bit of money from your blog...putting together a quality blog is challenging, and time is money, isn't it? I wholeheartedly agree with you about the "pay to post" subject. I tend to be less than forgiving on that point...if I'm at a gardening blog, and then all of a sudden there's a post about shower doors or some nonsense, it's unlikely that I'd ever visit again. I'm with you...I feel like the writer has compromised their credibility.