It might be helpful (since this triggers a lot of people all the time) to specify if you intend to Make the MC do it to others (Netori) [Nipponheads, please correct me if I use the terms wrong - srsly I hate that everything just gets Hentai terms these days, but ok, for communications sake...] or if it is done to them (Netorare).
So, in plain old english, if you cuckold other dudes and dudettes, or if you get cheated on and cuckolded by others.
Almost nobody has anything against the first (just look at all the games where female MCs get turned into allout cheating slutmonsters), but a lot of people have VERY strong opinions about the latter.
So, telling people you plan the first might actually net you some different fans, and allow you to cut down on all the Chill-Pills TM you'd need otherwise. Unless you actually do plan on the latter, which is fair enough - it's your effing game - but yeah, we know it will lead to butthurtses ;-D
Cheers!