There are several ways to tell if one is cheating. Cheaters often get greedy, let's say their first word happens to be eight letters long (which is possible if you started the game).
For example: If they used CITADELS (or its anagram DIALECTS), I can believe it once in a while but consider for a moment that there are over 200 combinations. In fact those two are the largest words out of all the possible combinations. Wouldn't words like CASTLE or STEAL be a little more believable?
How were they able to exhaust all their tiles on the second move? It happens but it's rare. Odd words are understandable, I know a few from Latin and Greek but if your buddy chimes in with "HEPTOSE" (especially on the first move)... really?
I'm not a sore loser because I have been creamed by people many times, they have earned it. However if you play someone and for a moment think: Okay, did I just play Geoffrey Chaucer as if he travelled time, entered this person's body and earned their doctorate from Oxford in Chemistry, Biology and Mathematics? I'm sure of it because this person doesn't normally pull words that spelling bee champions pull out of their ass.
If I know the person then I can usually tell because they all of a sudden start coming up with really good words that I know they don't know. I could tell when my friend Started cheating because out of nowhere they darted using really big hard words and getting a lot of points when before they weren't that good and would always lose with very low scores. So of the person just one day got really good at the game after not usually being very good then it usually means they are cheating.
I do not use the various word aids available. To me that takes all the fun out of it and does nothing for my brain! It is cheating. In Scrabble you may use a dictionary to check a word, not search for a word. So when people use these websites to get words they are cheating. One way to know if someone is cheating is if they consistently use all the tiles in a word or in a cross word. You may use all your tiles or most of them once in awhile, but when each word is a six letter word you know they are seeking help. It is not fun to lose any game but that is what sportsmanship and integrity are all about. To me that takes all the fun out of it.
I agree with Rebecca. I have a friend I just started playing with. My first games ever and I didn't know squat about playing the game. When this person emailed me, despite "Spell check", there were so many misspelled words in the text of the emails. Now, in Words With Friends, my friend plays words like zoeae, ululant, maqui, etc. The first game we played I ended up with something like 177 points and my friend had over 500 points. Come on. I refuse to use words I don't know, words that I don't know the definition of and that I can't use in a sentence. If that's the way everyone plays, assuming they are cheating, what's the point in playing that way? BTW, the second game we played, without cheating, I won. I just figured out some strategy and had better luck with letters. That or my friend let me win - who knows? Because there is no face to face in the game, integrity can be lost. What a shame that people cannot self monitor.
You don't need to have rules to know what is ethical. If you are using the official aids that WWF sells--fine. But those aids won't give you four 7-letter words in one game or bizarre Latin words. I don't understand how people can cheat, especially on something that is so meaningless. It is also counter-productive. If you play without cheating you will eventually get better and win on your own merits.