I’m no longer in an SEO-focused role necessarily (went from head of an SEO department to head of a general in-house marketing department) but in past experience I worked for an agency that insisted the only surefire way to build links was to buy them with a linkbuilding service like the Hoth.

FWIW — Complete fucking waste of money.

There weren’t any penalties, but the links would generally drop off of backlink reports within 6 months so any momentum you’d built up died down fairly quickly.

Ultimately though, Google doesn’t *really* have any way of knowing whether or not you paid directly to have a link on another site, and I really don’t think they care because there are so many “premium” directories out there (think WebMD, PsychologyToday, Angie’s List, etc). So unless you’re buying really shitty links from spammy domains, I wouldn’t expect any penalties because you paid a Mommy Blogger $100 to feature a link to your site in one of her articles.