There’s just no agreement about former CIA director Petraeus and emails on the Yahoo! front page.
It looks like one editor decided that the possessive of a name ending in S requires just an apostrophe:
Oops. Presumably someone else also employed by Yahoo! decided that the possessive requires an apostrophe and an S. Also, email doesn’t require a hyphen:
Oops × 2. Yet another editor likes e-mails (with a hyphen) and a return to Petraeus’ without that additional S:
While legitimate news outlets have an established house style (or follow Associated Press style), yahoo.com editors seem to be totally unaware of the need for editorial consistency. Associated Press style says that the possessive of a name ending in S requires just an apostrophe, and that there’s no hyphen in email.
It ain’t rocket surgery. It’s as simple as making a decision and sticking with it.