I pretty regularly read the Dear Prudence advice column on Slate.com. In one of her recent questions, a person said that they had received an "announcement" (from the way the person talked about it, it seemed like they were not verbal but were an actual physical announcement of some sort) that they were not invited to a wedding. The person was asking how to respond.
Apparently, it's a trend now to inform people they're not invited. Prudence was shocked to see how much of a trend it is and included a link to an article on ehow that suggests a bride should get together with people specifically to inform them they're not invited!
The ehow article included many other breaches of ettiquette including inviting the uninvited to the showers and utilizing a B list.
I had no idea this even existed! I can't believe people actually do this!
Here's the link to the Q&A if you're interested (it starts at the second paragrah)