There have been several "investigations" into Milesbar and it has been discussed quite a bit on flyertalk. From all indications, it is a scam. There has not been one single report of anyone obtaining free travel from this company. When the site was first introduced, Milesbar was using logos of various airlines on their homepage. Members of flyertalk contacted each airline whose logo was displayed and not one airline (from the Corporate Office to frequent flier department) knew anything about any agreement with milesbar. One airline, Northwest, initiated an investigation into Milesbar and shortly after that Milesbar dropped all airline logos from their site.
Investigations by flyertalk members also disclosed who the parties were that are behind the site. Because of the 09/11/01 event and "profiling" ethics I will not state here the nationality of those behind the site. However, this information is readily available by searching previous topics under ("spam") in flyertalk.