BT's Twitter competition plays cupid and encourages romantics to tweet their messages of love to the top of London's BT Tower.
But an ad for Ikea in Australia has become a social media hit, offering free cots to babies born nine months after Valentine's Day.
Supermarkets and retailers, including Tesco and John Lewis, have also taken the opportunity to promote flowers and gifts to last-minute shoppers.
Cadbury has a Promoted Trend on Twitter and other brands offering 140 character love notes include Citizen Watches, Royal Mail and Now TV.
— Cadbury Creme Egg (@CadburyUK) February 14, 2013