don't1) Lack of chargebacks:merchantsany transaction everThe inability to file a chargeback moves the burden of transaction risk back onto the buyer2) Difficulty in establishing trust in centralized playersoneizedall the time.severelyIt is literally easier to steal bitcoins than it is to steal any other asset in the history of worldlosePaper wallet / cold storageLocal walletsHosted walletsEscrow servicesExchangesDecentralized exchangesPrepaid Bitcoin cardsThe other answers seem to address the more general types of fraud that also apply to cash and other assets, such as theft and lack of chargebacks.I will use this answer to describe types of fraud that are exclusive to Bitcoin and similar block-chain based crypto-currencies.1.Malleability attacksIn the Bitcoin protocol, every transaction can be identified by a double SHA256 hash of the data in the transaction.This hash is called the txid.The transaction data that is hashed includes the amount of bitcoin in the transaction, the sender(s) and recipient(s) of the transaction, and a script and signature proving that the sender(s) own(s) the coins and specifying the conditions for redeeming the coins sent.

This hash acts as an identifier for the transaction in the network...but you have to be careful!The problem arises when a company uses the txid in an automated system to issue refunds for transactions that did not properly propagate the first time.Consider this scenario:A user withdraws their bitcoin from an exchange (oh say Mt.Gox generates a bitcoin transaction to send the user their bitcoin.This transaction will have a txid that Mt.Gox will store in their database.Gox's system will look at the blockchain sometime later and see if a transaction with this txid has been confirmed.If so, then all is good, if not, then they might automatically try to send a new transaction after some time so that the user does not get angry and say 'where is my money!!'.Here is where the fraud comes in!Let's say that I am a malicious user.I withdraw some bitcoin from Mt.When they propagate the transaction, I copy it right away and make a tiny, inconsequential adjustment to the script or signature by appending a specific set of bytes so that the transaction is still valid.

Note, the same amount of money is still being sent from/to the same parties.I just did the equivalent of drawing a dot on a package after it was weighed for shipping.It still has a valid signature from Mt.Nothing materially changes...EXCEPT for the txid - the double SHA256 hash of the transaction data.If I broadcast this 'malleated' transaction with the new txid into the network, it MIGHT get accepted before Mt.If this happens, then Mt.Gox's original transaction will never be seen in the blockchain because the coins will have already been sent to me and the transaction will be seen as an invalid double spend attempt.So, I will still receive my coins, but Mt.Gox's automated system will not see the txid of the transaction they generated in the blockchain.The txid in the blockchain will be that of the transaction I modified or 'malleated'.So the automated system may send me my coins again because it thinks that the previous transaction failed, effectively giving me twice the money.Of course this problem can be avoided through extra accounting checks, but it has a problem that has bitten some companies before.The risks of tx malleability have been reduced recently after updates to the bitcoin core protocol, but it is still important to be aware of.To read more about it, see the Bitcoin wiki.2.

Double Spend AttacksI might use bitcoin to buy some chicken wings from a small town, backwoods restaurant near Charleston, WV (yes, there is a place there that accepts bitcoin).When I pay for my chicken wings, I will send the proper amount  of bitcoin to the store owner's bitcoin address.bitcoin chessA short time later he will give me my chicken wings and I'll leave.If I wasn't a nice guy, when I sent him the bitcoin I might have actually made 2 transactions!will bitcoin go bustOne that went to him and one that went back to me.bitcoin atm square oneHe will have seen my transaction to him, but it will still likely be unconfirmed by the network at the time I leave.bitcoin usb boot

Now the bitcoin core protocol prevents this type of double spending, which is one of its claims to fame.It will only allow one of my transactions to succeed.So if i'm lucky, the transaction I sent back to myself will be confirmed and the transaction I sent to the store owner won't be.bbc bitcoin hackI'll be long gone by the time he realizes it!bitcoin leverage calculatorSo I will have tricked the store owner into thinking I sent him the money, when I really sent him what turned out to be an invalid transaction.This problem can be avoided entirely by waiting for a few confirmations in the network.bitcoin plugin chromeBut for instantaneous transactions, companies can use payment processors like Bitpay who check for double spend attempts immediately.It is always good to be aware!This answer doesn't cover everything, but I hope that somebody finds it useful!There have been numerous reports regarding the different types of bitcoin scams.bitcoin miner kickstarter

One of the biggest bitcoin scams ever reported was the Digital Bitcoin Company Fraud where Mr.Ho was accused of defrauding 49 clients based on the Taipei Criminal Investigation.This happened in May, 2016.Another bitcoin scam was when hackers stole more than $300k from one of the blockchain’s biggest VCs.Types of Bitcoin FraudBitcoin Ponzi Schemes –the case that involved bitcoin investment scheme ended when Trendon Shavers received 18 months in prison.cnbc bitcoin 100This Bitcoin Ponzi scheme case started way back in January, 2013 when authorities caught him doing his fraudulent BitcoinPonzi scheme through its Bitcoin Savings and Trust or BCS&TRegistration forgery- beware of websites claiming to offer bitcoin or any other cryptocurrency investment as well as mining services.A lot of websites are using forged documents such as in the case of Xmaxbit—a bitcoin site offering cryptocurrency investment and bitcoin mining services.