I couldn't figure out why the first item in the
openViewOnFocus address bar was always "Search with Google" despite having changed the default search engine. Initially I thought it was a bug but then it finally dawned on me that it was coming from Top Sites on the new tab page. Clearly I don't use Top Sites much but this connection would have been even harder to make if the user had changed the new tab page to blank or something else. Users will likely want to delete and alter these items, currently there is no obvious way to do so with the Top Sites association being entirely implicit.
I think it would be advisable to add a link (eg "From your Top Sites") in the listing that points to the Activity Stream page so it is clear what is being shown and where to go to customize it. This link should work even if the user has set new tabs to blank.