>
> You're still being unfair to bitcoin.  Not everyone who uses bitcoins will
> be dishonest.  The dishonest 5% hashing power is not going to be used in
> 100% of any given merchants transactions.
>

OK, sure, let's say most Bitcoin users will be honest (we hope). But
unfortunately in a situation where fraud is possible users wouldn't
necessarily distribute evenly over transactions.

Back when I worked on Gmail, we did a little study where we selected a
random subset of email accounts from Nigeria and waited to see if they
received abuse reports, showed up on dating site blacklists etc. It turned
out about 2/3rds of them did. This obviously doesn't imply that 2/3rds of
all Nigerians are scammers, but unfortunately the few that are are
responsible for a disproportionate number of account creations.

If a merchant is selling something of value repeatedly, then a small number
of scammers can go back and try their luck over and over. I'm not sure how
many trades fall into such an exploitable category, though.

Also, there's the philosophical question of how honest people really are
when there's no consequences to their actions. For instance, if most people
were honest, then piracy would be not a big problem. But game studios that
have cracked DRM quite often report piracy rates of 95%, i.e. for every 5
sales they make, they get 100 people playing on their servers - the vast
majority of their users are not honest.