Any of the above can be outsourced, it's just a matter of what you want to pay for it. Personally, I go for whitehat all the way...it takes longer, but it also delivers much better targeted traffic and the links have a much longer lifespan. Blackhat links are generally removed as quickly as they're found, and rarely get repeat visits because you're just getting traffic, not targeted and pre-interested traffic. Greyhat works a little better, but in most cases only minimally...if it resembles spam in any way, people don't touch it, and they don't like things that are not straightforward and directly related to what they're looking for. Whitehat links are welcomed on the sites where they're placed, and over time my percentage of repeat visitors has gone up to about 60-70%. Many visitors to my hubs have also been linking and recommending them to others, because they've been exactly what they were looking for. If someone applies this successfully enough, they can eventually get to the point where other people are doing a lot of backlinking for them completely free of charge.