I dont think you should invest a lot in it. Pay attention to what you do and stay cautious. Websites like these can disappear any time
If that's the thread title website you are referring to, bitcoin-trader.biz, is it nice and comfortable in the cave you've been living in?
Bitcoin is a commodity, not unlike gold. How often have you seen an advertisement "Put your gold to work, earn x% per day for depositing gold with us" ?
Your investment is the bitcoins themselves.
+1 on that, how many people would send their gold to someone anonymous on the promise that it would be returned doubled in a month?
This is the 'because Bitcoin' magic effect at work. From looking through the list of BT victims, the majority seem to have come from the fiat world and allowed themselves to be convinced that these patently absurd ROI's can be achieved simply 'because bitcoin'.
Life isn't like that.