we might say that economic nodes exert, at least, a large amount of control over the network. as far as i know, Microstrategy doesn't even hold their own keys, so the question is probably applying to whoever is holding their bitcoin for them.

i think if one actor holds 10 million bitcoin, it would be pretty horrible for the network. when a soft fork comes along, it's hard to see how the guys buying most of the bitcoin wouldn't be determine which side of the fork ends up being "the real" bitcoin.