Here's an old post on search engine roundtable that claims google's policy is to discount previous backlink juice when a domain changes ownership. I'm not convinced whether this is actually true or something Google says to discourage excessive domain buying / 301 redirecting for SEO benefit. The comments above seem to give varying opinions on this matter. Would be great to get to the bottom of that one!
Backlinks – These are basically anchor links present on external websites that take the visitor back to a domain. The higher the number and authority of backlinks, the higher the authority of a domain. For example, if a domain has a backlink from Forbes, TechCrunch or BBC, it’ll gain a lot of authority in the eyes of Google and other search engines. It’s like attaching a reference letter from Bill Gates to your CV.
Page authority ranking criteria are similar to domain authority. It’s ranked on a scale of 1 to 100. Page Authority measures the predictive ranking of a web page. The page authority of a website can change depending on various metrics. Search engines examine the relevance and authority of a page based on its contents and external links. If a webpage has links to higher authority sites and has keywords in it, its authority ranking will increase.
If you bid at NameJet *after* the domain name moves to Pending Delete status, then it’s too late for NameJet to take advantage of their relationship with eNom and take control of the name. So then eNom thinks, “no interest from NameJet users; we’ll just drop it” and it goes through the regular deletion process — where the fastest fingers can register it. In some cases, investors don’t want to pay the $59 or $69 fee at NameJet and if there are no bids they can likely get it for $18.99 at Pheenix or using other dropcatching services.
1) pending delete auctions. These are domains that were not renewed and are going through a pretty complicated drop process. You can backorder these names at the auction venues and then each attempts to "catch" the dropping domain. If one is successful you win the domain at $59 if you're the only one to backorder the name. If more than one person backordered the domain a 3 day private auction is held. Once the domain goes through the drop process, the back links have pretty much zero SEO benifit to the new domain owner.
Of course, this does not happen equally across the board. Some site owners are lazy and barely put in any effort. As you can probably tell, the four situations I outlined above probably will not occur for website owners who are lazy. Now, for website owners who put in the work and the time for their online properties, you can bet that they would get to benefit from the four situations outlined above.