This method at one time was used to try and resolve smart pricing. On a Friday ads would be pulled down and Adbrite put in its place and then Monday Adsense would be put back on as higher priced ads would technically show tell the Adsense bot crawled the pages.
The bot crawls quicker now so this not effective means of doing this. Also if I recall it violates there TOS in one way or another. So this is not advised. To do it once to try another ad network and then seeing Adsense was better and putting back wouldnt in my eyes cause a problem but doin it monthly or weekly would cause you some promlems.