If it strikes you as a little suspicious that so many cities seemed to crackdown on their Occupy encampments at around the same time, well, that's because it is. Earlier today Oakland Mayor Jean Quan admitted to the BBC:

I was recently on a conference call with 18 cities across the country who had the same situation where what had started as a political movement and a political encampment ended up being an encampment that was no longer in control of the people who started them...”

Not exactly evidence of a conspiracy per se, but certainly suggests that cities may have been sharing information about tactics and timing.

As for Seattle, mayor's office spokesperson Julie Moore confirms that Seattle did not participate in this call, which was apparently coordinated through the US Conference of Mayors.

UPDATE: Moore clarifies:

Seattle was invited to an in-person meeting by the US Conference of Mayors, which we declined. The conference call was pre-planning for the in-person meeting, and since we were not attending that meeting we were not invited to participate in the conference call.