Uh oh, you guys. We're getting word that the SFPD is throwing up barricades around the Occupy SF camp at Justin Herman Plaza. We don't yet know what this means, but a confrontation is clearly imminent.

Will the Occupy Oakland kids pop over to show some solidarity? Stay tuned.

Update, 5:15 p.m.: Twitterer @OccupyVideo brings us... well, video from Justin Herman Plaza:

Mayor Lee told ABC7 that the barricades were put up to "better define the boundaries" of the Occupy camp.

6:00: Police presence increases at Justin Herman Plaza:

6:40: And now? The barricades have come down. CBS 5's Joe Vazquez reports: "Strange situation at #occupySF. Cops aggressively put up barricades, then just as quickly took them down."

8:30: Protesters moved their General Assembly to the middle of Market Street in front of the Federal Reserve. Naturally, Muni service is being disrupted by the people in the street. Extremely rough estimates from cops on the scene puts the crowd "in the hundreds."