Having a flash video in a website is a poor choice, as flash is bandwidth heavy, which can cause problems for viewers on slow internet connections.
I differ, if the video is encoded at the right bitrate that won't cause any problem. You just have to serve the according bit rate for example, the flv have to be encoded at a lower bit rate for people who are using 56k modems, you will compromise the quality however. If it is being served from a flash streaming server you won't have to encode at different bit rates, just one and let it stream. To say flash video is a poor choice is not a correct statement, check some of the more visit websites such as espn, abc, cbs, they all serve videos..