There are people who drop prices of alt.currencies intentionally. From what I remember seeing on exchanges, I can make real conclusion: somebody intentionally work on drooping prices, they even put big money in it.
Who else has noticed? Who are "they" and why they do this? Maybe ASIC owners?
Eh, someone who instamines 500k coins with 50 mh/s and has no energy to sit and trade daily but would rather just get rid of them before the coin dies anyway.