It's not just five incidents of PayPal chargebacks. I know for sure, because I myself can count 4 different times I got scammed...!
I am not sure whether you read the update of our FAQ - but we cannot be responsible for the actions our users make. FYI - there have been only five scam cases on BitMarket. Since you sell quite a few coins there and you are one of the few sellers that still accept Paypal no wonder that it is you that got scammed (since our sellers who don't accept Paypal don't). Also, these scams only started recently (the very first one being the infamous Brian, from whom we managed to retrieve part of the stolen money/btc).
Immediately after receiving your email about new scammers, their account got blocked. Perhaps you didn't receive a response straight away (but you did receive it, I wrote it myself on the 3rd of August - advising you, again, not to use Paypal).
Surprisingly in 4 out of 5 cases - the scammer was the REAL owner of the bitmarket/ebay/email account. We know this, because, for examlple, one of them said she never heard of bitcoins and yet, she was selling them on ebay (the stolen ones from Bitmarket, among others probably). In hope of getting some assistance I wrote the people on ebay that she sold the coins to - and only one responded. I asked him to help us and tell us the address of the person, so that we could try and even go to the police, or at least provide our users with her details. Unfortunately, the guy asked me for 10 BTC in exchange for revealing her details; that was very disappointing, not like the old days when the Bitcoin community was a bunch of honest people who supported each other free of charge. So, I said to this person that we may give him the 10 BTC after (and if) we get anything back from the scammer. He then got back to me with the address of his Bitcoin related website and tried to exchange her address for email addresses of Bitmarket users (wanted to do some, as he called it, "marketing"), which I found even more disappointing and gave up talking to him.
So, please appreciate that we REALLY tried to do our best in chasing every single scammer; but it's just beyond our power (the same way it was beyond Mt. Gox and CoinPal). Also, you have no idea how much time it costs us to stay up to date with all emails. We receive 50 support mails everyday, which have to be handled directly by myself or M4v3R, because April has no access to the admin panel due to security reasons. On top of that - we get 50-100 verification requests, 75% of which requires us to further communicate with the people, since they have no CoinPal, no OTC, no ebay feedback. Every evening and every weekend I spend 2-3 hours doing responding to support emails. Every scammer means a lot of additional hours for us, so please be a little bit more understanding.