When a new user hovers over the workspace switcher they should be presented with something helpful, not just the prompt 'click to start dragging ...' or the workspace name; users should not need to care which number workspace it is and drag and drop of windows between workspaces is not supported in compiz anyway.
This functionality was already present in some of the earlier hardy alphas but was removed for some reason in later alphas (it may have been in 2.19.4-0ubuntu1 but the version no. and time of release does not make much sense). Apparently the work was done by MacSlow, more info and an out of date patch exists here: https://wiki.ubuntu.com/DesktopTeam/Meeting/2008-02-07?highlight=(pager). A uptodate image is available here: http://people.ubuntu.com/~mmueller/tooltips.png. All of the patches and diffs needed to implement it should be here: http://people.ubuntu.com/~mmueller/
it was too buggy that's why it was removed take a look to bug 204994, bug 207693, the inclusion of those changes needs more discussion , better to raise this on a mailing list or in the brainstorm website, thanks.