Active Building Permits in Seattle

The housing boom may be bust, but Seattle is still bustling with active building permits. Robert Morton found this data at data.seattle.gov, the City of Seattle's public data repository. Using his viz, you can see permits going back several years. What's going on in your neighborhood?

For me, this data brings up questions about the City of Seattle permit process. For instance, dozens of buildings downtown (I am assuming commercial spaces), have a "blanket permit for interior non-structural alterations - Administrative permit only- no work authorized". So, why issue a permit that cannot be used for anything? I am sure there is a good reason, I just can't figure it out.