while i agree that it is, or at least was, a fake holiday created out of thin air by PR flunkies. if enough online retailers believe it exist, they don't want to be left out and so they start having cyber day sales. take, for example, this screen shot i took from amazon.com this morning:
when retailers treat the monday after thanksgiving as a sale day, people probably will start to do more online shopping that day, because it's the day with all the sales. cyber monday may have started out fake, but it eventually will become real, if it hasn't become real already.
this is probably also how "black friday" got started, way back whenever. sometimes the media can create reality.