Google representatives state that webmasters should never ask for links, and that this behaviour is against their guidelines

One of Google’s most recent posts on the Portugese webmaster blog has stated that not is is the practice of buying links against Google’s guidelines, but the mere act of asking for links also against their terms of service.

The author from Google, Diogo Bothelho, stated:

“não compre, venda, troque ou peça links,” which translates to “do not buy, sell, exchange or ask for links.”

This is consistent with comments from John Mueller, who has in the past advised uses to “avoid link building altogether”

Some SEOs feel that the goal posts have been moved slightly with regard to what constitutes unnatural linking. However, Google’s position seems quite clear, where any actions that a marketer takes which primarily for the acquisition of links that pass on PageRank will deemed as penalty worthy.

Ultimately with all forms of search engine marketing, there is going to be a degree of some form of risk. For those that want certainties, that their site is going to rank high if they do x or y, SEO is probably not the right game for them. Actually, for anyone who wants certainties, marketing is probably not the right game for them!