I've recently experimented with incorporating top search terms into my blog titles and posts to see what kind of impact it would have on traffic. I've already made some interesting observations.
When I simply put the three top search terms into a title and the article had little or nothing to do with the terms, very little impact was seen. Normally a blog search will display a bit of the article, and if the subject matter isn't what the searcher is looking for, they're not going to click.
On the other hand, when I wrote a story related to the a popular search term such as Whopper Freakout, I saw very significant traffic increases. However, if the search term is too "hot", like "Prometa" was after the CBS interview on the topic, the effect is diminished. I assume this is because there are thousands of trend watchers out there using these terms as well. One should also keep in mind that the hot search term right now, may not be so hot 20 minutes from now.
I guess the moral of the story is that it's worthwhile taking a look at top search trends before you start writing a post and if you can incorporate a word or phrase into the title or body, go for it. But, if you want to retain consistency and value in your blog, it still has to be good information consistent with your blog's theme.
If you use your blog as an advertising vehicle for other sites, you also have to determine if increased traffic is resulting in increased business. Who's your target audience? Is the subject of your post something related to their interests?