what exactly is deemed an unnatural backlink profile this week?
That's just my hypothesis on why a couple of sites I'm used to seeing have disappeared. If you analysed the backlink patterns for the top 10 before this mess started for a particular 2 word term in my niche. One site stands out. Far more links to it than anyone else, more of them from US sites even though the product is very specific UK only, 301s from sites that had backlinks that included wiki spam, blog comment spam etc.
The other 9 have far less backlinks with around 80% from UK on topic sites. If you were to graph them they would all fall around a line except that one that wouldn't fit on the graph paper.
Bizarrely one site that is ranking now is an exact keyword domain with links back from around 100 domians almost exclusively paid directory networks. You know the sort of thing, pay $99 and get into 34 directories, $199 for 100.