1) the lineage can't always be known, and sometimes people lie 2) someone can easily convert FLAC > wav > mp3 > wav > FLAC, so the distribution format isn't always a guarantee.

Take a look at the lossy or lossless sub forum in technobabble. People post spectrum and frequency analyses screenshots in order to determine if their show is truly lossless. That's the only fail safe way to know for sure if it's truly lossless.

Some shows get pulled for being lossy. I'm not sure how often it happens, but I've seen a few shows pulled here at TTD that were mp3 sourced (but shared as FLAC), and a video that was mpeg1 sourced (but shared as an authored DVD, which is required to be mpeg2). So there is a little pollution still happening.

But I don't think that spreading mp3s on rapidshare or similar for those who want them is a bad thing. A lot of ppl listen to low fi systems (iPod ear buds, cheap computer speakers, etc.) exclusively these days so they probably wouldn't be able to tell the difference anyway. They get to hear the shows, for free, in a relatively high quality format compared to yesteryear. Those are the most important things IMO. www.archive.org has FLACs as well as mp3s available for download for a lot of shows.