Almost every yoshinkan dojo does the 150 or so basic techniques...each of these has atemi and are standardized. You can find a good sample in almost any of the good yoshinkan texts out there. If you don't block the strike and move, there's a fair chance a yudansha would pop you if you are at an appropriate level for that. Many of the techniques trained outside of the 150 basic techniques will also have atemi.
The atemi most often trained will be the attention punch, a punch with the raised middle knuckle to the short ribs, almost an upper cut kind of punch designed to come in 'under the radar', a sliding backfist which is similar to the previous one. Often instructors will note (and have you try gently) elbow strikes to the ribs while entering and turning for kaitenage or sankajo. I've also been taught some sweeps, a kind of blocking kick to the thigh as uke is coming forward, using the entry as atemi, etc.
At different times, all of these may or may not be acceptable in different ways (like anywhere else). For instance, if I am working with some under 3rd kyu, and I pop them in the nose the third time I do a sankajo entry under an extended arm and cause them to bleed, I'd better be up on my ukemi the next time I'm called up...and my blocking too...
Its pretty much case by case...I've had classes where the whole point was to get you used to getting hit (and not freaking out). I've also had classes that were all basic movement and rudimentary technique because there were first timers and we didn't want to scare them away the first night.
Aikido technique is generally trained in a kata or kata like form. As a result, people will get upset with you if you deviate from the form in unexpected ways without a prior agreement with your partner, and the understanding of the instructor responsible. Seems reasonable to me...
Ron, there are tons of dojo's with people who don't have a clue what the "real world" is or what a "real fight" is.... and they simply don't want to know. Aikido is a haven where they don't have to face the real world, in a lot of cases. They consider demo's to BE the real world.
Its no more a haven than 90% of the other dojo out there...I'd say of the dojo I've seen overall, only the top 10% of any style are really serious. BJJ and MMA training may be the solid exception. But even there, the serious places place constraints over where, when and how hard striking contact can be. Not to mention the use of protective gear. You can't take all the ills of MA today and drop them in aikido's lap...the problem is much bigger than that...and you know it.