I was trying to implement this, it's not so that difficult, but with a problem, I have no easy way to stop people from spamming the faucet with different subdomains, e.g. one hold example.com would use aa.example.com and bb.example.com pointing to the same site to apply the faucet payment, I have no good way to determine if they are the same site, and one may generate infinite subdomains as long as he own the domain name.
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After talking to Ranlo, no easy way to determine the popularity of a site could be found. So you could only pay people for a link on a domain homepage. That is all that is required for the current domain faucet bounty.
Later on if there is more interest, a subdomain faucet bounty would be added for you to make tracking code, or give more money to sites that you manually verify, and then your faucet could also pay for subdomains and/or pay more for popular sites.
If we're talking about the value of backlinks, why not use Google's own metric, which is Google Pagerank? It's their measure of how powerful a domain is - Facebook has a pagerank of 10 while some minor sub-domain with no links has a pagerank of 0. It's an exponential scale - so a site with pagerank of 1 is ten times more powerful than a site with pagerank 0, a site with pagerank 2 is 100 times more powerful than a site with pagerank 0, etc. Also pagerank is calculated on a page by page basis (i.e. they don't just assess the domain. So you can look-up the exact page with a link to devtome.
See the following page for how to pull the api for Google pagerank:
https://code.google.com/p/seostats/
But why would we take PR as being a value of anything? Nobody uses PR as a true value of worth of a domain. It has a very slight impact on some things, but is nothing to worry about. A PR0 site can easily outrank a PR10 site going for the same keywords, depending on how each of them is optimized.
Don't be fooled by the FUD put out by Google Pagerank still rules. I have a lot of websites - and while their content is excellent they all need backlinks to rank, and high pagerank links too. Forget about domains - always, always assess pagerank by individual page. Sure a PR0 page from a PR10 domain may be outranked by a PR0 page from a PR0 domain if the latter has better onsite SEO. But a PR10 page will always outrank a PR0 page unless the former has been manually penalised by Google.
I was proposing assessing the incoming links page by page rather than based on the domain.
This isn't the right place for this discussion I guess, but you are entirely wrong in your assessment. Do you need some backlinks to rank? Actually, this is also wrong, :p. Though backlinks do help. But ranking has absolutely 0 to do with PR. You can have a PR10 PAGE that is outranked by a PR0 PAGE. It all depends on how you have it optimized.
Ranking is still largely about the links coming into your page. I understand that this faucet is about incoming links not the PR of individual devtome pages. The best way to assess incoming links is via pagerank.
Re the PR10 page being outranked by a PR0 page - care to share any examples? I've survived Penguin and Panda and a whole host of algos and ranking is largely due to the strength of the incoming links regardless of the FUD put out by Google.