Adsense Question

I've noticed something lately with Adsense that I find a little frustrating, and I am wondering if it's always been this way and will continue.

The way Adsense is supposed to work is that it crawls your site's content and populates your ads with site appropriate content. I find this works well when my blogs are viewed as a hole (i.e. more than one post per page).

However when traffic comes via links to specific posts (only one post is displayed on the main blog page), then the ads are no longer site appropriate. They seem to default to ads for "blogging", which is not what my blogs are about.

If I have a reader arrive from, for example, a link posted on Twitter about a diet post, they're not going to have any interest in the "blogging" ads. They're looking for weight loss information. Those weight loss ads only appear if the reader clicks on the blog header ("home") to generate more posts on the page at the same time.

Is it because my posts are short and Adsense doesn't have enough per-post content to crawl to populate the ads? If you have Adsense on your blog(s), what has your experience been with this issue?