If only 'Thumb Up' will remain, uploader won't be able to see that someone had disliked his release. If he won't see it, he wouldn't do anything to correct the defects what became the reason why someone disliked his release. I think it will cause more bad releases.
Also, there are Flac releases what were re-encoded from MP3 (or other lossy formats) to lossless. You can detect false FLAC or re-encoded MP3s via spectral analysis.
p.s. Why don't you use Vorbis? It has much better compression level than MP3.