I think you mean. "can and may".I have been feeding mine crickets for a year now and have not had one single cricket bite either my frog or me.
Even if a cricket did bite his frog it would probably only be 1 cricket and therefor 1 bite mark. Unless he is raising mutant hostile crickets that all team up to swarm the frog but... I think he would notice that.
*coughs* But in all seriousness pictures would be very helpful.