First off, when I pressed "submit feedback" on pony.fm, I didn't expect that a full-blown public topic will be created instead of direct conversation. I've become aware of this topic only after I got an email notification that I was mentioned x.x
Now, on the topic of lossless-only. I am having no problems with lossless uploads since I always render wav (my DAW doesn't allow lossy renders, thankfully). I am more concerned about other musicians that use DAW's with direct mp3 export option -- asking them to go back and rerender in wav might be too much of a step and I've already heard some concerns in private conversations about that. It's easier to ignore this site for them than battle with an old project that might not render exactly the same way because of hardware and software changes/upgrades/updates/reinstalls.
Until all DAW's magically will disallow rendering directly into lossy formats, this will continue being an issue.
Don't forget that sometimes an MP3 can be the only thing left -- projects can be lost in big crash (happened to PinkiePieSwear), synths can be resold (happened to me) and rerender can be no longer available.
I wholeheartedly support lossless, don't get me wrong.
But please consider the fact that brony musicians aren't the bunch that got their act together of having multiple backups of everything, rendering always in lossless, and keeping lossless copy of their music handy.
Bandcamp is in position of denying you source of income if you don't upload in lossless. Pony.fm doesn't have that luxury.