As for your options, in Canada we have an ironic situation. We pay a tariff of $0.29 per blank CD, which money goes to a collective, which holds it for an astonishingly long time (how much they collect is regulated, what the collective does with it is left unregulated), and then gives it to music and sound recording rights holders. It is legal in Canada to copy a sound recording for personal use.
However, Canadians do not know about the tariff, and do not know that they can copy legally. So they either copy, thinking they are breaking the law when they are not, or pay iTunes, and pay for their recordings twice.
Merry Christmas to all.

“No firecrackers went off when the compromise bill was cleared Oct. 1, the last day of the Congressional session, and no bells are likely to ring when President Ford signs the measure some time this week. The matter is simply too technical, complicated and cumbersome for anyone but specialists to get very excited.” (emphasis mine)

The copyright regime created in 1976 assumed that if copyright was of concern to you, then you were making a commercial use and you had an army of lawyers at the ready. It was not designed as a system that was intended to apply to everyday individuals. No one can expect the public to comply with a copyright system that has only gotten more technical, cumbersome, and complicated in the last 30+ years.

We would choose (a) and (c). As to (a), we long have felt reliable, unbiased, comprehensive access to copyright education was a problem, so we started a sister site Core Copyright [http://corecopyright.wordpress.com/] as an act of public scholarship.

As to (c), we are writing about 21st century normative copyright expectations as evidence of a frame shift that currently is colliding with the long-embedded frame of “piracy.” An initial peek into this research is available at http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1392914

Personally, I tend to think that efforts to “educate the public” about copyright law, while widespread, are doomed to failure and, potentially, are counter-productive. The better result would be to make copyright law actually make sense in a way that the public could easily understand.

If you buy into what many people (incl., e.g., Jessica Litman) have written about the growing importance of the common person in the scheme of copyright law, it is clear that enforcing a statute drafted and understood primarily by publishing industry specialists is no way to organize the standards of individual liability in this area.

So, in short, I see no harm in putting a “no infringement intended” notice on a mashup. The upside may be minimal or non-existent, but so what?

And so, I think, those notices may not exactly be evidence of what you claim they are.