Some early adopters have large numbers of bitcoins because they took risks and invested time and resources in an unproven technology that was hardly used by anyone and that was much harder to secure properly. Many early adopters spent large numbers of bitcoins quite a few times before they became valuable or bought only small amounts and didn't make huge gains. There is no guarantee that the price of a bitcoin will increase or drop. This is very similar to investing in an early startup that can either gain value through its usefulness and popularity, or just never break through. Bitcoin is still in its infancy, and it has been designed with a very long-term view; it is hard to imagine how it could be less biased towards early adopters, and today's users may or may not be the early adopters of tomorrow.
Yes. History is littered with currencies that failed and are no longer used, such as the German Mark during the Weimar Republic and, more recently, the Zimbabwean dollar. Although previous currency failures were typically due to hyperinflation of a kind that Bitcoin makes impossible, there is always potential for technical failures, competing currencies, political issues and so on. As a basic rule of thumb, no currency should be considered absolutely safe from failures or hard times. Bitcoin has proven reliable for years since its inception and there is a lot of potential for Bitcoin to continue to grow. However, no one is in a position to predict what the future will be for Bitcoin.
© 2016 bit2.biz