[jwdunne]

I think there is shameless and there is shameless. I don't see the examples the OP mentions as being shameless really. Perhaps riding on the back of a notable death or otherwise serious, negative event is shameless. For example, in the UK, we recently had a roller coaster crash. An accident solicitor sent out a marketing SMS along the lines of "Have you been involved in a roller coaster crash? We can help claim the compensation you deserve". I would say this is an example of taking shamelessness too far to the point where it's disrespectful and ultimately harmful to your reputation.

[WalterSear]

IMHO, it's a slippery slope, and it's a poor mindset to be in.

If you need to take advantage of your audience to get their attention, they will not trust you, and the effectiveness of subsequent messages, and the subsequent sale you are pursuing will be colored by that adversariality.

My personal anecdata, but I've watched 'not respecting your audience in pursuit of attention' fail catastrophically several times. It's a popular way to screw up.