Thats why you should take a look and speculate on which coin is likley to gain the most of % upward trend. Yes you should learn a lot - crypto currency markets can be manipulated and abused a lot, specially for some coin that has low value (I am talking about pump&dumps). As most coins don't have any use cases you can ethher hope that they will have some in the future or just look at them like some ponzi/pyramid scheme. Lot of people started their own cryptocurrency just to earn money and they stashed enormous amounts in their wallets, thats why I said earlier that it is a gamble, online exchanges like poloniex and bittrex are like big casinos.

Don't get me wrong I don't say that all coins were made for this purpose for the devs to get rich, but some of them, good percent, are. Thats why you should be careful. Don't just buy single coin because somebody told all the best about it, rather think clearly.

Word scam: because some people that have invested their money in particular coin are likely to try to do free marketing for them so that they can see profit. Other people who haven't invested in a good time/ or that think that particular coin is bad will call it a scam. Different opinions from different people, this happens.