The point is.
100 bitcoins, say 250.000$, receive 100.000 lumenst that at current price is 5000$.
Imagine some of the bitcoin holders sell.. and price goes down...
I think almost nobody with 250.000$ in bitcoins will care about 5000 or less $.
These giveaways has a second effect, unused giveaway lumens will go to stellar.org. And i dont think they will sell as crazy. I see it fine, they are making a nice work and i belive their aim is not to became "more" rich. For that they could simple use ripple.
There are inner things in stellar design i was thinking about a long time and now it is real. It will have a future. Dont worry about that.