Study shows Facebook most active Wednesdays at 3pm ET

I'm not sure I would agree with the implication that this is the best time to post something. From the viral launches I've run (most recently through youtube.com/laughpong), around 10am ET tends to work really well (don't have enough data to talk about days, but Wednesday sounds pretty reasonable).

The advantage here is that at 10am ET most people on the east coast are at work, not asleep or commuting. If you can get a decent enough spike there, about an hour later people from the Central time zone will be in that same position, and then an hour later people from Mountain time. Then by 10am Pacific time there's another spike from Pacific time and from people on the East Coast starting to take lunch.

The "lunchtime spike" rolls from east to west coast like your initial spike, and by the time it hits the West coast, your "after work" spike is about to start.

By timing it right, you can potentially catch and ride all three waves of people who are looking for things on the internet. Just like in surfing, if you can catch the wave just right you can ride it for a long, long time. An essentially whole-day spike is a lot better than a massive spike over a very short period of time.