No, those websites are pure scam. There is no way to double a Bitcoin without doing anything because this is exactly what they do: nothing.
They just use the funds coming from new sign ups to pay those who joined before. Then once their system collapse after some days they just open a new website and do it again. Or just publish fake "latest withdrawals"
Sometimes they forgot to edit their FAQ etc so you can see the name of their previous scam in. Often you can see a badge "online since 465 days" but the domain name has been created 1 week ago
Double bitcoin sites are the same as just HYIP sites, re-tailored to cater for Bitcoin...If you looked into the ownership of these sites, you'd find that they have owners who have likely run HYIP scams before
Its more reliable to get into mining,I have tried it out with Genesis mining it worked well their return rates and period taken to complete the process is quiet resonable charges are a bit high but you will get good returns.
zaragro wrote: However, you can't expect to double your money. Other ways like HYIPs and Faucets is etiher to risky or not giving enough return.!
While you aren't going to double your money or make yourself rich with faucets, they are (thanks to the current value of Bitcoin) comparable with PTC ad values....1 US cent is about 250 Satoshi these days which, with the right faucets, can be earned in a few seconds. I use a series of sites which gives between 2 and 4 cents every 10 minutes (for clicking 7 captchas every 10 minutes)...not going to get rich but still better than nothing