It's all about Natural & Semantic web now!
The algorithm is smarter time by time, your SEO building should too!
1. 15 backlinks from PR4 to PR9 (root domain) social sites
-Strong natural Social backlink are what search engine valued now
2. Manual work done with web browser only
-crucial for long term website SEO developing with clean building record
3. High PR Authority web 2.0 social signal boost
- stumbleupon likes, pinterest pins, reddit votes etc
4. Exposure to targeted audience
-category & keyword optimized for better traffic chances
5. Quality links that stay long!
-done on sociaI sites that meant to share url
6. Approved method to get index well & Google SERP (search engine result page) ranking boosting
7. Google Hummingbird, Panda update friendly & will always safe on future as search engines love social shared content.
8. All links will be submitted to indexers for quick indexification
Backlinks from 15 PR4 to PR9
Manual Authority Backlinks from 15 PR4 to PR9 Social Bookmarking Sites