You might end up playing a cheater at some point (though it's uncommon). But you're much more probable to end up playing someone better and you'll think they're a cheater..

Look at this livestream where Magnus Carlsen, the world champion, is logged in under another account and crushes Jan Gustafsson (another grandmaster) and he can't believe it's a human playing him :) (or at least suggests he is skeptical)

https://youtu.be/Ka5sh6hBvSI?t=219