I know several people here who would love to take more interns but aren't allowed because it would take work away from their union employees.
I suggest that those people double check the labor laws. According to the US Dept. of Labor, an employer can offer an unpaid internship as long as their program meets the following conditions:
The training, even though it includes actual operation of the facilities of the employer, is similar to that which would be given in a vocational school;
The training is for the benefit of the trainee;
The trainees do not displace regular employees, but work under close observation;
The employer that provides the training derives no immediate advantage from the activities of the trainees and on occasion the employer’s operations may actually be impeded;
The trainees are not necessarily entitled to a job at the completion of the training period; and
The employer and the trainee understand that the trainees are not entitled to wages for the time spent in training.
You can find more information about local labor laws
here. Certainly, offering internships can tricky for the employer, but if they choose to do so, it can be accomplished and the unions (if they are good at all) should be supportive as it their mission is to support labor workers. What better way than to have well trained and informed future workers?