If it's anything like Twitter, it will appear in your stream out-of-sync with when it was posted, so it's guaranteed to appear near the top of your stream whether you're viewing it days after.
Why in gods name would I want to pay to market to people who like my fb page? Those guys are super fans already, and I almost certainly have their email address. As much as I appreciate fbs intentions in making advertising unobtrusive, this holds no interest for me as a marketer. I want people who have not bought my app to see my ads; that's how I get paid.
Seriously? You can't think of the possibilities for a business to utilize this?
Think about a company you would "Like". Imagine they offer a new product or have a sale. This ad would appear, and their already-fans would flock to it.
> or one of your friends must have interacted with
This is where I stop clicking "like" on anything (I already block facebook's scripts outside of facebook itself, so don't see their "like" buttons on external sites).
I'm not giving fb's advertisers permission to plonk adverts where my contacts will see them - if I think something is worth mentioning to my contacts I'll mention it myself. If someone places an advert on my news stream because I interacted with their page, then fair enough (I can just hit unlike should I choose to terminate that "relationship"). If fb want to advertise something to my contacts "just because" then they probably have the right to do so (no doubt this is covered in the Ts & Cs we agree to by creating an account and logging in), but I don't want to be a source of (an excuse for) advertising opportunities and won't be used as one.
It is funny, but I actually use it to block things that technically isn't ads almost as much as I block ads -- stackoverflows 'notification' bar, bitbuckets 'you have not validated your email', G+ stupid 'interesting stories that you properly care more about than your friends', etc.
