If you take the usual precautions, Greece is a safe place to travel and you're more likely to suffer from heat exhaustion or sunburn than from any kind of crime.
Adulterated drinks (known as bombes) are served in some bars and clubs in Athens and at resorts known for partying. These drinks are diluted with cheap illegal imports that leave you feeling worse for wear the next day.
At many of the party resorts catering to large budget-tour groups, spiked drinks are not uncommon; keep your hand over the top of your glass. More often than not, the perpetrators are foreign tourists rather than locals.
The touristikí̱ astynomía (tourist police) work in cooperation with the regular Greek police and are found in cities and popular tourist destinations. Each tourist police office has at least one member of staff who speaks English. Hotels, restaurants, travel agencies, tourist shops, tourist guides, waiters, taxi drivers and bus drivers all come under the jurisdiction of the tourist police. If you have a complaint about any of these, report it to the tourist police and they will investigate. If you need to report a theft or loss of passport, go to the tourist police first, and they will act as interpreters between you and the regular police.