I was shocked to see a bunch of reviews for car rental agencies I have never heard of, but nobody's thought of adding in Sixt which is definitely the largest rental agency in Germany. There's Europcar which is Europe's largest, but Sixt is all over Europe too.

As you'll notice, Epinions is largely US-based. For instance, half of the Canadian Provinces/Territories aren't in the database, so missing things of a significant magnitude aren't at all uncommon.

However, if you were to fill out one of the Category Leads' SAP request forms, they'd presumably be able to get Sixt added to the database (assuming you'd review it...).