I feel like a handful of people could basically ruin the entire site by constantly creating new accounts and offering to buy/sell Bitcoins but then not showing up to trades. This attack doesn't cost anything other than a bit of time. LocalBitcoins would then be very difficult to start using because no one would ever trust users without previous trades. Is there anything in place now or planned to prevent this?
Even trades and ratings are free to fake.
Not really on localbitcoins.com. Only the trades which have used the localbitcoins transaction/escrow feature can gain reputation/feedback. Also we keep now also track of the trading volume of inviduals, and this is shown on the public profile (not exactly for privacy reasons, but if it is under 25 BTC, 25-150 or above 150 BTC).
As far as I remember the escrow works without fees, so where does it cost a scammer to fake transactions?
To be honest I don't totally trust lb to not loose my bitcoins so I traded more than 150BTC with people I met there without using the escrow. I now have a list of people that I can contact for future trades without even touching lb. I know I might damage lb or my own profile on lb by not acting as planned but loosing 100BTC is not an option. I only do in person trades and it always works like that:
We meet, we chat, we go to a cafe, we show cash, we send the bitcoins and after the first or second confirmation pass the cash. If the business gets more hectic some day and chatting 20minutes with some stranger about bitcoin becomes annoying, and lb is in business much longer, I guess your escrow (or any other well known green address) will help streamline the process.
On the other hand we have gotten lots of feedback that leaving feedback without using the escrow/transaction should be possible. On the other hand, all kind of one-time accounts, crappy ads, etc are a problem already. If we allow leaving feedback without any kind of confirmation that a trade has actually occurred, it would probably turn the system even more worse.
lb for me is a listing of potential scammers that I have to be very very careful with when doing a trade. The escrow as the only thing that adds value to the actual transaction is of no value to me. Any green address would do as I do in person trades and these work by sending the bitcoins first anyway.
If you want to add value to using lb, you could take deposits. Merchants could be listed also by the deposit they put into lb. This deposit would get a 2 weeks delay when withdrawing it, so a merchant scamming others would risk his deposit in case these others can proof to you that they were scammed. Sadly this requires trusting you to not run with the money but multisig can help. The funds will be released as soon as both your and my sig confirm the return of the funds. If you refuse to sign (usually for 2 weeks but on dispute this can be extended indefinitely), these bitcoins essentially get destroyed. I would favor this over you holding the bitcoins putting you into the position of holding many many bitcoins to potentially "loose" although this way the victim can not be paid with such funds.