Salesforce.com is sharpening its software development efforts with a new team from social bookmarking startup Clipboard. Clipboard and Salesforce.com announced the acquisition Thursday, in a deal which has pegged at between $10M and $20M. Actual terms of the buy were not disclosed. Clipboard was a developer of a social bookmarking and sharing service. The firm said that, as part of the buy, it will shut down its services on June 30th, allowing users to download and save their bookmarks. Clipboard's backers included Acequia Capital, Andreessen Horowitz, Betaworks, CODE Advisors, CrunchFund, Draper Fisher Jurvetson, First Round Capital, Founders Co-op, Index Ventures, Scientia, SV Angel, and Vast Ventures.