Are you thinking of using a VPN to bypass DNS hijacking by your ISP (as described in Redirecting DNS for Ads and Profit and Middleboxes considered harmful: DNS Edition)?
Then think again.
A new paper titled “A Glance through the VPN Looking Glass: IPv6 Leakage and DNS Hijacking in Commercial VPN clients” by Vasile Claudiu Perta, Marco Valerio Barbera, Gareth Tyson, Hamed Haddadi and Alessandro Mei, demonstrates that many commercial VPN operators are at it too.
The paper will appear at The 15th Privacy Enhancing Technologies Symposium and is available online now (open access copy linked).