I know that SpatiaLite is a lightweight solution. Would it be a problem if I put it on a 5K pageview/day site? Is PostGIS too resources-consuming for such usage?
The dataset is something like < 100MB.
Are there any other factors you would consider in cases like this?
I don't think the number of page views is particularly important. What matters is the operations that go into each page view. Unless you are doing something pretty complex then either is likely to be OK (or you have a design problem, which will probably make either perform badly).
In general, if you have a serious multi-user server need, I'd probably go with postgis. If you have a simple desktop requirement, spatialite will probably be better. Postgis is definitely what you want if you have serious scale-out needs (e.g. multiple front end servers working with shared data) - spatialite can't do that. Otherwise, use whatever you're more comfortable with, leaning towards spatialite and sqlite as being easier to set up and manage.
