That sounds reasonable. Even 40 would be superior to 20. My first thought was that The Sun would probably just DDOS the top 20 and do whatever it wants while they're flailing.
If a government wanted to force a take-down of the steem blockchain for whatever reason, killing 20 servers would seem like child's play.
If a government wanted to force a take-down of the bitcoin blockchain for whatever reason, they'd really have a difficult time and they'd probably have to invest a ton of cash into developing their own highly-specialized server farms.