For example it is indeed true that:
100$ invested in 2010 would give you back 75 millions now, but
100$ invested in 2013 (december) and you will "only" have 350$ now.
It's very easy to pick the right investment when you're
looking back. Therein lies a big risk: people tend to easily assume it will continue, the recent altcoin bubble is a nice example of people jumping on the train because of FOMO (fear of missing out).
Common sense dictates anything that increases 10% per day in value can't last.