I sometimes get carried away and build links too fast, but my first ones are usually from very high page rank so haven't been sandboxed yet.
I agree with all the above comments, getting a lot of links in one day or a week makes Google's left eyebrow lift up rather like Roger Moore's (007). So do it gradually so it looks natural to Google - hey they know what we do do but don't wave it in their face if you know what I mean!
The biggest mistake I see is link exchange as a whole. You shouldn't need to do it. If you do it means that your site is not very good. Build a good web site that people would want to visit and return to. A site people would want to recommend to their friends and colleagues. Fill it with original and compelling content. Then call the organisations or informational sites in your niche who have high PR. CALL them don't email them. Talk to them, tell them what you do and where you want to go with it. Show them how your site or product can benefit from being mentioned on their site and how they can benefit from you. Ask them for a link. Do this daily with as many companies as you can. It doesn't just have to be companies in your niche. Local newspapers or magazines. Charities. Whatever. Give them a story. Be creative. You need fewer good quality links to rank well. So get to work and develop these. Develop relationships with the people who link to you after this. Call them regularly (once every 2 or 3 months) and keep it moving. They will recommend your site to other big PR sites. This is how linking should be done.
If you are not targeting right keywords for link exchange then your whole efforts goes waste...............
Yeah, and shouldn't be poverty in the world too... You talking about the perfect internet, an Utopic internet. But even if you have a good site, you DO need to develop to be stronger than the spammers. Anyway, the greatest content always win. If it doesn't, Google lose credibility. Then Google loses money. And Google doesn't lose money.
Targeting the wrong keywords in the anchor text. I see this error all the time. Before starting your link building campaign you should choose the right keywords.
The worst is getting a bunch of links not related to your niche. When I first started out with no experience in SEO and link building, my initial thought of is to get as many links as possible and that does not matter where it comes from as long as it is links. That was a mistake.