Last modified: 2010-05-15 15:38:50 UTC
The SVG renderer currently seems to render the image at the specified size, then resizes it as a bitmap, resulting in poor-quality upscaling and overly-aliased downscaling. Though not a major concern for Wiki software, it would be a worthwile improvement to embrace the use of vector graphics over bitmaps. See: http://en.wikipedia.org/wiki/User:Ktims/Sandbox/SVG for example.
You've requested a rendering larger than the natural size of the image, which isn't allowed to avoid resource-hogging.
Especially on commons, I'm not sure this is a good idea. Many vector images don't have a 'natural' size and their size is determined by context. I think it would be more appropriate to base the resource limitation on absolute size instead. For iconography, the natural size might be quite small, however the ability to increase the size losslessly may be useful. A minor thing in any case.