THE SAN FRANCISCO Chronicle ran a lengthy article March 25 on the battle over housing at the Presidio that once again left out the crucial point: The Presidio is no longer a national park. It's a privatized business park, run by a private trust that is accountable to nobody, with a mandate to generate as much revenue as possible.

That's why it's somewhat silly for groups like the Sierra Club (which, through its Presidio Task Force chair, Michael Alexander, helped promote the privatization of the Presidio) to complain about proposals to replace the housing that's scheduled for demolition.

The biggest problem at the Presidio is the fact that it's been turned into a commercial center, dominated by the likes of Lucas Film, which will bring 1,400 employees to a new office complex on the site. The small nonprofits that initially occupied some of the remaining military buildings are getting forced out by rent hikes. And the existing housing is available only at market-rate rents, which makes it too expensive for the people who work on the former army base.

If that housing is going to be demolished, it ought to be replaced with units that are (at the very least) affordable to the people working at the site. The last thing San Francisco needs is more big developments, attracting more people, with no offsetting housing construction.