No, all of your friends and co-workers haven't disappeared. They just can't chat with you via Google Talk.
It appears the popular chat service went down Thursday morning.
From Google's website just before 7 a.m.:
"We're aware of a problem with Google Talk affecting a majority of users. The affected users are able to access Google Talk, but are seeing error messages and/or other unexpected behavior."
Google also issued an update at 7:50 a.m.:
"We are continuing to investigate this issue. We will provide an update by 7/26/12 8:50 AM detailing when we expect to resolve the problem."
And another at 8:50 a.m.:
"Our team is continuing to investigate this issue. We will provide an update by 7/26/12 9:50 AM with more information about this problem. Thank you for your patience."
So until the problem is fixed, you may actually have to make eye contact with the guy in the cubicle across from you.
We'll update when we find out more.
UPDATE: Looks like Google Talk returned for some people by 10:30 a.m. There is still no official word on a cause of the outage from Google.
At 10:50 a.m. Google released the following update:
"Google Talk service has already been restored for some users, and we expect a resolution for all users in the near future. Please note this time frame is an estimate and may change."
FINAL UPDATE: Service has been restored! You don't have to talk to people in person anymore!
From Google at 11:25 a.m.:
"The problem with Google Talk should be resolved. We apologize for the inconvenience and thank you for your patience and continued support. Please rest assured that system reliability is a top priority at Google, and we are making continuous improvements to make our systems better. If you are still experiencing an issue, please contact us via the Google Help Center."