Google released a major algorithm update aka 'Penguin' on April 24.
This algorithm update targets websites that don’t have very high quality content and/or have had their ranking signals over optimised.
Many web masters have been penalised having too many inbound links from link directories and low quality domains.
If you intend to use an SEO company, make sure you know what is their link building strategy.
The tradition way of link building will almost definitely have Google black list your domain.
Your link building strategy should include one way inbound links from websites with quality contents.
Also the link building process should be a gradual process.
Just having a text link will not work any more.
Websites linking to you should have an article relating to the page of your website they are linking to.