Popular with smaller jets (think bizjets) because the structural issues aren't so great with smaller engines and fuel savings not as large an issue in bizjets ops compared with airlines. Also putting the engines at the back leaves a clean wing with more of the leading and trailing edges available for high lift devices - which is a big issue for bizjets because they often operate into smaller airports.
The philosophy of putting the VC10's engines at the back was to leave the whole wing available for the flaps and slats. The aircraft was designed to operate into BOAC ''Empire route'' airfields such as short, high and hot Nairobi. The VC10 had approach speeds some 20 knots slower that the B707. Boeing got round this by getting the US government to fund longer runways at the places thier potential customers would need to operate. This made the VC10 look heavy and expensive which is one of the reasons why it wasn't as successful as the 707.