Amazon themselves are the ones offering the streams as options, so I don't think it's attracting any more attention by downloading the CBR stream than it is downloading the VBR stream in the first place. That's like saying downloading 1080p attracts more attention than downloading 720p. It all comes from the CDN servers anyway, so at the end of the day I don't think it matters one way or the other which bitrate, resolution, audio format, or subtitles you download. Just my two cents.