Bitcoin has a number of practical advantages for ordinary e-commerce

That may be true, but it also has disadvantages such as scalability. AFAICT, every Bitcoin node must maintain an up-to-date ledger containing all transactions made to date: obviously, this is unsustainable in the long run.

The "fixed number of bitcoins" policy is also an issue. According to Bitcoin developers, having more miners makes the network more resilient to attack, in addition to speeding up transactions. Eventually, the subsidy to mining activity will become too low and agents will need to partially replicate its effect with transaction fees. This is sobering enough for a network which touts free transactions! as a selling point; however, what's more worrying, resiliency will also drop dramatically as mining activity slows. Paying a mining bonus would be more fitting, since the benefits of increased mining are shared by all holders of bitcoin.