I saw a presentation from Heroku where they discussed using a similar
paradigm, and they ran into trouble once they hit a couple thousand
databases. If memory serves, this was on an older version of
PostgreSQL and may not be relevant with 9.0 (or even 8.4?), but you
may want to try to track down one of their developers (maybe through
their mailing lists or forums?) and check.
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Maciek Sakrejda | System Architect | Truviso
1065 E. Hillsdale Blvd., Suite 215
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www.truviso.com