I run a couple of low-volume, niche-specific sites. I run ads on them, from that big search engine company. I was recently told that my account was terminated for "invalid clicks", with no further details. I can only speculate that someone overenthusiastically clicked many, many ads. Searching the web a bit on the topic seems to indicate that's exactly what has happened to many, many others.
Suffice it to say, this irritates me mightily. Even though my account is evidently permanently "disapproved", the ads still show. Of course, they certainly have the right to ban anyone, for whatever reason they like. So be it.
I'd like to find an alternative. Is there an alternative? What I liked is that the ads were relatively low-key, and were (usually) on topic.