EMPLOYEE1There may be some hacks on the Flash front where people have written their own decoders (ie., for OGG), but those come with some fairly huge limitations (cross-domain security restrictions, 100% parse/decode up front = high CPU use, lag, RAM use etc.) - so I don't recommend using any of them.
Adobe have announced they will be adding support for the WebM container format, which includes OGG/Vorbis (VP8 I think it is, off the top of my head, for video, and OGG for audio) support. I don't think FLAC is in there, but that would mean a possible way to get support for the OGG container via Flash 10-point-something for browsers which don't do OGG (cough cough, Safari.)
Bandwidth would be another big consideration for streaming data like this, of course.
On the HTML5 front, it may be possible to add support to your browser via plugins in the way you install system codecs etc., for FLAC. I have OGG support in Safari for example, since Safari uses QuickTime to play HTML5 audio (and video) and I added the OGG plugin to QuickTime.
Sounds like you can have FLAC in an OGG container? The WhatWG site lists this an example...
<source src='audio.oga' type='audio/ogg; codecs=flac'>
Of course, that would be subject to having a FLAC decoder installed. Whether installing a general "Ogg support" codec/package would include FLAC, I have no idea.