In reply to Oogachooga:
We had our van more or less emptied by thieves in Sperlonga on the Amalfi coast. (Though for some crags in the area you can park in a café provided you eat/drink there before or after climbing).
Sometimes you can park more safely in villages (e.g. Grotti), tourist attractions (e.g. Toraino) or at the foot of the crag (e.g Ferrentillo)
Northern and mountain areas of Italy such as Val Pennevaire feel less risky in general - but you can get unlucky anywhere.
Re Sardinia, we last took our van there 15 years ago. We wild camped without problems but things may have changed since.
Hope you have a great trip. It can be a worry when you've got your life in a campervan but it's well worth it!
Post edited at 19:43