Recently, I re-conducted a study with my fellow analyst to prove if self-social bookmarking can help Google ranking. Below are considered :

a. No onsite work done, site update and link building done- this is to ensure that any ranking improvement is due to social bookmarking.

b. Ranking data before any social bookmarking is gathered. This is to assess ranking improvements.

c. Seven social bookmarking sites are used in this study with different for each site and a total of 28 keywords in the study.

Del.icio.us
Simpy
Technorati
BlinkList
Stumble Upon
Google toolbar bookmarks
Digg
NowPublic
Spurl
Furl

d. Only one person account has been used in the bookmarking process so this means it is a form of “self social bookmarking”.

e. Then all the data are gathered in the period of one month.

Results:

Statistics of the result shows that 64.29% of the keywords did not improve in ranking, 32.14% of the keywords have very slight increase in rankings which we could consider as insignificant. And only 3.57% have significant increase in ranking.

This suggest that self social bookmarking is not heavily weight in Google as it is a form of self-promotion. Although this study does not cover several bookmarkers but social bookmarking by different people in different geographical locations really means that your document is important and highly valued.