That pipe is from logic used in
header.php of TwentyEleven (and many others) it takes for granted that the site will always has a Site Title AND a Tagline ( which will be used in title tag too ).
Your site doesn't have Tagline.
Why not ? just go to the setting page and enter something ( keywords ) relevants to the site, the Tagline or is also useful for search engine, there is no benefit on missing out on this one.
In addition to that, there are bugs (or whatever you call it) in
wp_title() and is in process of improving, see these tickets
Add a better option for
Do not prefix
wp_title() with spaces if
$sep is empty