A couple of things.
1. I have had sites penalized and now if you ask they will give an example of a link that may be causing a penalty. 100% of the time (for me) the example they have given me was an anchor optimized link. Never have I been shown a link that was generic or plain anchor. This may not be the case for everyone, but it is for me.
2. Another point, if you listen to Google they have all but devalued every single link type but if you listen closer you know this cannot possibly be true.
Why would I say link spamming will get you penalized (no matter where the links are coming from) if links don't have value? If links do not count, they simply would not count, they could not push you up or down either way if they had no (or little) value.
3. Some people are saying guest posting has been sliding for quite some time, yet my former employer (65% guest post links) is ranking in the top 20 for almost 1,000 keywords and it goes up each and every month. But they work with HUGE brands and they do no low rent or shady stuff. The articles are written by professional writers, the quality is impeccable, the articles find homes on extremely high authority sites and the guest posts requests are sent by an individual to hand picked sites. No automation involved, just a huge budget and lots of time.
4. The sites your links go on and how you frame your links will make a difference. If your link in the body of the article about blue widgets is "
Blue Widgets" and then in your bio you write "Joe Smith buys all his
Blue widgets from Blue Widgets.com", then you dont understand what Guest Posting is. If your article about blue widgets has a link that looks more like this "
maybe these items will help with your widget problems " which points to bluewidgets.com and your bio says "Joe Smith is a freelance blogger and you can
find more of his opinions here" and that also points to your bluewidgets.com site then you are not optimizing text and not forcing keywords into an article. Besides, what self respecting blog owner wants a keyword optimized article when all they are looking for is great content for their readers.
Last but not least, at one point every single TYPE of link has been penalized. Guest posts, blog posts, web 2.0's, article submissions, profile links and others yet there are thousands of sites that rank with those exact links. Some get smacked others stick around, why? The appearance of the link is what matters and where it is coming from also matters. A good site with traffic that places your non optimized link on it WILL help with traffic and it will also help with rankings and why wouldnt it? As long as Google's Algo values or devalues links, then links will still be a (and maybe THE) major factor in ranking. If they remove links as a factor, I am pretty sure we will all know very quickly.
Thats just my 2 cents, take it for what it's worth.