“Do MP3 compressed samples decompress into RAM when downloaded into a web browser player such as Flash or Beatnik? If so how much RAM do they use? And is it a good idea to downsample and convert stereo to mono to minimize the amount of RAM the decompressed sample occupies?”
Some codecs decompress files as they are read. MP3 players really only “decode” the MP3 data, an important distinction from decompress. When audio is encoded as MP3 data the extra information is discarded, and not included with the file for later use. Further, the players are designed to be able to stream the audio from a disk or website, so RAM is only an issue for the application you are using, not so much for the data itself. If you have enough RAM to run the application efficiently you are fine. Nevertheless downsampling the files or reducing them to mono will create MP3’s with less data that are even easier to read.