Paid links are an incredibly gray area. What exactly is a paid link? How can Google figure out what is paid and what isn't? Google's Matt Cutts dove into the topic paid links in a webmaster help video.
Because of this, there's where it can be hard to determine if a link is paid. on what exactly a paid link.
Incredibly Clear Paid Links
There are definitely a lot of cases where it is painfully obvious to trained SEOs when a link is paid or not, even when some webmasters think there being pretty clever about it.
The vast majority of the time things are incredibly clear, people are paying money outright for links based on PageRank, flowing the PageRank, trying to get high the rankings," Cutts said. "Ninety-nine percent of the time it's abundantly clear that these are links that are being bought and paid and sold and all that sort of stuff."
But then there's the gray area. What if someone's not paying someone for a back link, but instead the company takes them out and buy them pizza and beer in exchange for that link or story? Does it become paid then? Or where is that line? Cutts continues and tries to explain the differences.
1. Value of the Item
Is it swag you picked up a conference such as a T-shirt or a pen? That likely isn't going to sway your opinion on what you write about the company. But things range in value from cheap pens all the way up to things of high monetary value, and that's where things get tricky. And what about gift cards for smart ones that fall into the realm of things regarding paid links.
Sometimes people might say something like, "Hey, I'd like to send you a gift card.' You know what gift cards are pretty fundable you can convert them to money and back and forth... On the other hand, something like "I'm going to give you a free trial of perfume" or "I'm going to buy you a beer" or something like that, that's less of a connection.
But we do look at how close something is to actual money when we look at those kinds of things. If somebody goes and buys you a dinner and you write a blog post four months later, and the dinner wasn't some huge steak dinner with 18 courses ... that's probably not the sort of thing we worry about, as you would guess.
Read more : http://searchenginewatch.com/article/2332787/Matt-Cutts-Shares-4-Ways-Google-Evaluates-Paid-Links