Well another project a bit more elaborated then the usually doublers running it may let some people to double but others wont see a satoshi from it.Its more risky then any thing,and you main investment will return after two years.
These are not even investments, Everything offering double on a period of weeks is just too ridiculous to even call scam, I find it amazing that some people still fall to this kind of traps even with users telling people not to use these sites.