Aim? IM? Aim for? I'm not entirely sure what the question is here. However, if it's that they're IMing, that could be entirely platonic and they're just being social. If they're actually aiming for strangers, then it could be that they have some internal issues that they're dealing with badly. The vast majority of people who cheat don't do so because they see some flaw in their partner (in fact, many have extremely attractive partners) but rather because they personally have a low self-esteem, some form of self-hate, or some toxic feeling of entitlement going on.