Since launching last April, Facebook Chat usage increased steadily to reach the 1 billion per day mark beginning the week of June 15, 2009, according to Facebook engineer Chris Piro.
A result, Piro said, is increased communications between Facebook users.
"As an engineer it's exciting to launch a product used by so many people, but it's even more rewarding to watch it grow week over week and month after month," Piro said. "There are still improvements to make and features to launch, so we still have plenty of work to do."
Since launching Facebook Chat, Piro said their engineers have worked to improve the client's load so it could accept more concurrent users and reduce failures, such as the dreaded "red box of death."
"We've invested a lot in making Chat stable and scalable in the past, and we continue making improvements even now," he said.