In order to properly deliver an atemi the individual must know how to properly punch/kick. Atemi are an important part of Aikido training but all to often it is neglected. As mentioned previously, in OSensei's day the vast majority, if not all, of his students trained in other arts and knew how to strike. Today that definately isn't the case. In some instances there are instructors that simply do not know how to strike and therefore teach it incorrectly or do not teach it at all. The emphasis during training is generally spent trying to work on the technique and striking is left out as it clutters the training making akward movements that much more akward. All that being said atemi should definately be taught but more importantly how to strike should be taught.
Agreed. We've started a youth class at our dojo. Since the students are a little too young to dive right into Aikido we've based the curriculum around karate basics. Trying to get them fundamentally sound with striking is important for their Aikido.
Occasionally, in the advanced adult classes, we will have free form practice where the Nage has no knowledge of what type of attack will be presented. I find this type of training the most helpful and challenging. The idea is to relax, let go, and react in some way...even it's not perfect. Aikido, at least my Aikido at this point, looks quite different when you practice this way.