Scams and scammers are everywhere in Vegas. Taxi drivers automatically take "tourists" from the airport the long way to their hotel. Upscale restaurants pad their bills (look for the extra entree or extra drinks), especially if you've been drinking. If you Valet park your car, leave nothing of value inside. They can and do check trunks and glove boxes. You may encounter someone walking who claims to be broke and needs to sell either his "gold" ring, "gold" chain or his "Rolex" watch. Don't buy any of this crap, even for $20.
There's more but this will give you an idea of how "scam city" operates. Also, be extra careful when gambling. Always be aware of where your cup full of quarters is when playing slots. Someone will distract you, while their accomplice steals it. Same goes for purses, one of the most popular types of thievery around the slot areas. Be careful who stands next to you at a dice table. You must protect your chips in the rack. Same goes for someone who sits down next to you at a Blackjack table. Never take your cue stick to the bar and set it down ANYWHERE! Bye bye cue!
Do you want me to go on? DONT' GET INVOLVED WITH STRANGERS! They are not your friends! Every year MANY people get robbed and killed in hotel rooms. It is one of Vegas' best kept secrets. Parking structures are also good places to get robbed. Walk in pairs! And be extra careful crossing the strip, especially at night. The street is full of drunk drivers. Someone was killed last year in front of the RIV, crossing from the MacDonalds! And finally, in case you didn't know, the downtown area is dangerous at night. Don't go alone!
P.S. One more - the Strip clubs are the worst rip off joints in the world. All of them! If you must have sex, go to an Asian massage parlor. It will cost you $100-150 but you won't get ripped off. Even there you must negotiate.