It's not the only place.  Ginestar has a big problem as does El Perello and recently there has been a spate of thefts in Tres Cales (near L'Ametlla de Mar) and Gilet (near L'Ampolla).

One possible reason Bitem/Tivenys is more prone is there is effectively 1 road in, 1 road out (unless you fancy a scenic ride to Benifallet). So, keep an eye on a house.  Wait for the owners to go out and get your mate to keep an eye on the road to/from Tortosa.  If the owners come back a quick phone call and you have 10-15 minutes to make your escape.