With free stuff, you get what you paid for... Using free VPNs have few disadvantages. For example, a standard weak encryption of only up to 128-bit (PPTP) for most of them or no encryption at all, which is very bad for your own security. While a paid VPN use strong encryptions, Open VPN, for example, has double with up to 256-bit encryption through OpenSSL.You use a more secure Internet connection. Free VPN often have a low speed as well most of the time.