Mining underlies (basically) the same risk as any other type of investment in my opinion. As Cryptocurrencies are still not approved as payment mehtod by many Countries, there is a large risk of exchange rate fluctuations as we currently see very well when looking at Bitcoin. China says "NO", BTC drops. Starbucks (or any other company for example) says "YES", exchange rate climbs up, altough not with similar impact as if a whole country would accept a coin as a valid currency. High Risk => High Payout/Loss

Industrial revolution? - Maybe. Most Coins are based on Hashing Proof-of-Work algorythms that don't actually generate something thats usefull for other aspects of our everyday life. But there are some coins which have at least the right approach, Primecoin for example. Altough I personally have no real benefit from knowing a Prime number with 300 Million digits, these numbers are at least usefull for Sercurity systems as long as the master pattern for generating prime numbers won't be discovered.

I'm currently mining them too, as they are relatively safe from being overcome by GPUs or ASICs for at least the near future and allow for a stable payout expectation. This has - in my opinion - the additional advantage that I won't have to buy and build my own minign rigs, but that I can rent servers to participate on the calculation process instead.

But there is still a certain risk left, altough said aspects are very unlikely atm.