A Google Webmaster Help thread has one webmaster asking if it would be a bad thing for him to use block-level links in his HTML5 web site.
First let me explain what it is by referencing HTML5 Doctor:
Imagine you have a front page with lots of teasers for news articles, each of which leads to a page devoted to the full text of that article. Obviously, each story needs a heading and you’ll want an image too, and you’ll want them all clickable. In current mark-up you’ll probably have something like this:
<div class="story"> <h3><a href="story1.html">Bruce Lawson voted sexiest man on Earth</a></h3> <p><a href="story1.html"><img src="bruce.jpg" alt="full story. " />A congress representing all the planet's women unanimously voted Bruce Lawson as sexiest man alive.</a></p> <p><a href="story1.html">Read more</a></p> </div>
Note that you have three identical links (or two if, like the BBC News site, you assume your readers don’t need a “read more” link).
In <abbr>HTML</abbr> 5, you code it like this: <pre><code><article> <a href="story1.html"> <h3>Bruce Lawson voted sexiest man on Earth</h3> <p><img src="bruce.jpg" alt="gorgeous lovebundle. ">A congress representing all the planet's women unanimously voted Bruce Lawson as sexiest man alive.</p> <p>Read more</p> </a>
Now the single link surrounds the whole teaser, removing duplication and creating a much wider hit area to click.
Google's John Mueller kind of cautioned against using this technique. He wrote:
That usage would be fine with us - we'd still pick up the link, and would be able to associate your text as an anchor with that. We're pretty flexible with parsing HTML, so you could probably even use this with HTML4. That said, the clearer you make your anchor text, the easier it is for us to understand the context of the link, so I wouldn't necessarily always use a whole paragraph as the anchor for all of your internal links.
In short, since the whole paragraph is one big link, there is a ton of anchor text to associate to the link. So it may be confusing for Google to understand what that link is really about.
Forum discussion at Google Webmaster Help.