Bah to "infinite resolution", or even 15MP.
Even the highest quality 35mm ekt you can get your hands on today will yield *crap* @ 15mp resolution. It will be grainy and ugly (when viewed @ 100% screen resolution). If you're scanning from a 4x6 print, it gets far worse. When you're scanning for large format prints from 4x6 chemical prints, you would typically max out at maybe 400dpi. After that, you'll get much better results using edge detection software (like Genuine Fractals) to increase the resolution, rather than trying to get more data by scanning in at high resolutions (2400dpi or something crazy).
But this is only for industrial stuff. For home use, going no larger than say 11x14, scanning from a 4x6 @ 300-400 dpi should be fine. Naturally, it won't be as good as scanning a negative, or better yet a chrome, but it should be acceptable. Note that of course file resolution shouldn't be equal to printer resolution. IE: there's no need to resample your 8x10 to 1440dpi, just because that's what you're printing at. On any modern inkjet printer, there's a practical sharpness limit where you won't be able to percieve anymore than 200dpi.