Yes cryptocurrency is already another option of payment and it's spreading like wide fire.
Alot where initially critical about cryptocurrency some labeling it all sort of names like a ponzi scheme, fraud etc but it has actual caught there interest

But want thing I can say is that we might see this giant companies like the OP has just mentioned that accepts cryptocurrency or some that has not yet started following the same way as facebook and creating there own coin.

Should there be a limitation to this yes cryptocurrency has created an avenue for a whole new way of trading and transaction should any company just develop there coin just because they had already gained fame and altcoins that has been in cryptocurrency for a while would die out this would cause competition and might build of to an avalanche of coins in the future.
bitcoin and some good number of altcoin are my point of fancy in the cryptocurrency community. am not interested in Libra coin(still sceptical about it)
If this faint want to venture into cryptocurrency there should make use of the existing coins and not corrupting the whole system