There's a list at theholidayspot.com/valentine, a website for thrifty lovers offering freebies including Valentine's Day-themed virtual greetings, desktop wallpaper, games and recipes.

The couple are also co-founders of Crowdrise, a fund-raising charity website which is currently helping generate funds to help the Japanese Earthquake and Tsunami relief fund.

As couples become couples, Facebook data scientist Carlos Diuk writes, the two people enter a period of courtship, during which timeline posts increase.