if receiver will spent that money (for example buy some goods on ebay) how can Paypal charge it back? Or Paypal will put customers account to negative balance?
If your Paypal has no funds in it and a charge-back occurs, this does not protect you from consequence. When your Paypal is negative they will encourage you to fund the account for awhile, but if you refuse to do so then they will take legal action against you. I don't know how these things work in other countries, but in USA you will likely end up with a judgement against you and they will forcibly remove the funds out of your paycheck through government intervention; seen it happen many times before.