I think, This is depends the keywords position.

I think its 4 to 10 Pr is good..

high page rank social bookmarking sites helps to increase better keyword rank results.

you can submit 10 Bookmarks in a day

maximum 10 per day...

I think submit 30 high PR website . its enough

Well do minimum bookmarking at least 10 per website. To save your self over optimization.

i think you can be post more then 10 in a day with high PR websites.

I think don't do mare SBM.. it should count as over optimization .. so PLZ do min sbm per day and diff sites.. Thanks

Sometimes we do more than 20 social bookmarking per day.Is it harmful for the site?

Need high pr and do follow social bookmarking sites provide keyword ranking.

I think you can submit more than 20 high PR and location wise Bookmarking sites.

Social bookmarking sites helps you to index your web page quickly with targeted keywords and boost your ranking in different search engines.

submit 15 to 20 bookmarking submission per day and also check that sites are whether do follow or no follow. Don't submit no follow sites.

Not to hijack the thread, but I"m curious- How diverse should I be when doing social bookmarking. For instance, if I post daily on StumbleUpon, Digg and Delicious is that enough? Or should I be doing more social bookmarking sites?