Google has been bolding the search phrase within the search results for as long as I can remember. For example, a search on [search engine roundtable] will bold the words “search,” “engine,” and “roundtable,” on the Google search results page. Here is a picture of one search result for that search phrase:

But according to a WebmasterWorld thread, Google is not always bolding words. I have confirmed this to be true, in some cases Google will not bold an exact matched phrase, in the Google search results. Why? I am not sure. Especially after seeing the latest Google blog post on search quality describe how Google will not only bold exact matches in the search results, but also implied matches, such as with a search on arod, which matches on and bolds “Alex Rodriguez,” picture:

So which examples can I show you that do not bold? How about my fun big blue pineapple chair example. Notice that in the third result, the title is not bolded:

That is just one quick example. I have seen more and I bet I can trigger more.

We have seen Google not bold URLs in some cases, and Google AdWords started bolding matches about a year or so ago. Even Google China bolds, but they bold in red.

Is this a bug, is there something more to this?

Forum discussion at WebmasterWorld.