I used %%componentdescription%% in meta description in group forum. My description contained quotes which weren't converted to ". As a result it broke the markup of the page.
It showed something like this:`
<meta name="description" content="Whether you are buying a new, never-registered domain name, negotiating to acquire a domain name from another person, or perhaps want to trade domain names, buying a domain name is a critical step. The "buying domain names" discussion forum can help with any questions you may have during the acquisition process." />`
As you see this breaks the markup... the quotes should be encoded using either htmlentities() or htmlspecialchars().