I don't agree because they have no incentive to be corrupt. The money lies into taking this product as far as it can go. we can never be 100% sure, but I believe they are clever enough to see this and I trust them because they are incentivized to behave.
The "winner-takes-all" outcome is also not a problem for me because the winner is the best content creator. People don't sign up to social media to make money. I don't care about curation rewards. But I also don't want a centralized company to make money out of my attention, and above all I hate adds. This is the value proposition that steem offers today.