Most typo3 installations have their template files stored in a subdirectory fileadmin/templates/. Searching for this string on google returns a hugh number of urls pointing to the template files of the website beside the websites really talking about template issues of typo3.
A simple but effective solution is to place a robots.txt in your root that marks your template directory as disallowed for search engines. Even if a view craweler ignores this directory, the most important ones like google take care of it.
Btw: An .htaccess protectoin of the template directory is no solution while it still needs to be accessible for referenced resources like images, stylesheets or scripts.
# Example robots.txt