It could be more than that. Vodafone broadband Internet (used to be UPC) is down in all of Czech Republic since about an hour. Their website is down (vodafone.cz), their mobile Internet seems slow. Coincidence?
I looked up Facebook IP address and tried to go there directly, bypassing the DNS. No response.
(I don't care about Facebook much, it was a test. WhatsApp though I have to use to communicate with relatives.)