TL;DR at the bottom

First, we can establish that cheating as a society is morally taboo. Second, we can observe that in the beginning few seasons of this show, as far as we know, everyone is faithful in their relationships. As time goes on more and more cheaters are exposed. Ex: Pam and Roy/Jim, Jan and Michael/Hunter, Angela and Andy/Dwight, Donna and Coach Shane/Michael, Angela and the Senator/Oscar, Ryan and Kelly/multiple girls, Kelly and Ravi/Ryan. Looking at this correlation, I believe prolonged exposure to being filmed morally corrupts people. That being said, Meredith has never cheated on, been cheated on, or been used to cheat with. She is therefore one of, if not the MOST wholesome person in The Office.

TL;DR- the cameras cause moral corruption as time goes on in the show. This makes cheating easier for everyone being filmed. Therefore, Meredith is wholesome and pure.