9. No shows when meetings are arranged. Half arsed excuses afterwards that are clearly not the truth.
10. And last but not least, indicating that you are open to friendship as well as looking for a relationship, but then backing out of this because you've got your own life already and are really only interested in a relationship. If you don't want friendship, then don't indicate it on your profile!
There are others. Indicating that you are single when you are not. Factual inaccuracies - false names, different locations, different careers, or pretending you've got a job when you don't. (Ok, why not just leave the field blank?) Another no-no is using somebody elses account. Don't laugh: an ex did that one to me, twice, to organise affairs.
Cultural coverups. Indicating you are out when you are not, pretending to have no children or not be married. Misrepresentations in general.
And finally, the worst of all, messaging somebody you already know, but haven't recognised!