Personally no - but we did meet a swedish couple in Gouvia (Corfu) a couple of years ago who claimed that the locals had poisened her own dog, plus a puppy from another boat a couple of weeks beforehand. The Greeks don't appear to be big on dogs.
Had a dog onboard, in Spain, Portugal and France, no problems atall, as long as you respect the other peoples privacy and don´t allow your dog to bark half the night or allow it to foul the pontoons or surrounding area or even the beach, some beaches will not allow dogs on them atall, but at night? who sees you?. Always carry a plastic bag and if it does pee on the pointoon, which they sometimes do, wash it off immediately. The greeks don´t like dogs period, so you may well have to be careful there.
Forget it! Yes, I know you can get them pet passported - but friends of mine on a years trip to the Med with their Westie, report that having the dog on board is spoiling the trip. In Majorca they were continually abused by other boat owners (Germans), refused access to the beach and ended up keeping the dog permanently on board. Minorca was a bit better. Greece is a no-no- they hate them.