I can't imagine that getting that filled OTC reasonably close to the mark would be serious trouble. Germany managed to sell 50,000 BTC without much trouble a few months ago.
Then again, it may be serious trouble if you have serious issues explaining the source.
MtGox also sold 60,000 BTC.
That’s 5% of the daily trade volume. Shouldn’t be an issue.
Except trade in bitcoin is fee-free and mostly regulation-free, so there is a lot of wash trading.