With the changes taking around with Google panda, penguin, Hummingbird & other birds, are businesses still buying links ? Is selling space in the form of link a viable business model for quality bloggers anymore ?
Whilst there may have been a small drop-off link buying is continuing much as before, especially so in all the tough niches (i.e. gambling, insurance, pharma, etc.). That being said, in my experience in the gambling niche most buyers have become more discerning in terms of the quality of the sites . Factors like domain & page authority, page rank, domain age, whether it's an established site with an existing following, etc. are all being looked at. As for whether it's a viable business model for quality bloggers...I would say it's a risky one. You'll mostly get offered a good fee for publishing links if your blog is strong enough but to make that your primary business model isn't really viable unless you have (a) very strong domain(s) or a lot of relatively strong domains. And then you better expect pagerank and ranking penalties once Google does catch up with you....how long that takes would of course depend on how careful you are as a publisher.
Link selling market is still active but with several updates from Google is has been effected a lot. Buyers are mostly looking for quality sites/blogs for link placement. The value of PageRank is not been that effective nowadays. A site needs to have good number of indexed pages, good numbers of backlinks towards it, and age of the site also matter nowadays. Since, there are many link sellers now so it has been more competitive. But, if you can provide quality content on a regular basis to your site then the site ranking will increase gradually then also adding social media to your sites will bring more value as well. Also, you need to improve on the DA/PA of your site which really matter nowadays because most link buyers prefers to take link from higher DA/PA based sites. So, I would suggest to be a active in this competitive market one should must focus more on his/her sites quality. As far as I concern, these two are the primary factors which can really boost up the health of your site for link selling business, 1 - quality content ans 2 - good DA/PA.
Regarding buying links in websites: basically if google finds out, you're out. obviously it applies specially to bulk link sellers/buyers.
As google evolves, I think, the link placement will also evolve. One entity can't control the entire market for long, the way Google is trying to do. Adwords can't be the only way of search marketing as everyone is being made to believe by Google. But in this mayhem, spam advertising will be wiped out for sure. Let us see what future holds for this industry.