facebook isn't the only social network out there.

But they are one of the most popular and the best place to advertise such projects and products. They have the best traffic next to google.

Well, I think existing ICO pages are remaining, but without ads, just for conversation and any updates for community

Only those paid ads are not allowed by facebook but when is that effective? Is someone here still seeing those paid ICO ads on their fb profiles?

What effect do you think this will have on ICOs and future of cryptocurrencies?

Actually its a low effect although its one of the best way to raise awareness to such projects so awareness will be slowed down.