I read that drop down menus have ill effects on SEO and that it might cause unnecessary PageRank 'leaks'. Will the page rank leaks ever be necessary?

Page rank leakage is the when outbound links distributed to the internal pages. It refers reduces your websites overall page rank. There are three ways to prevent page rank leaks:
1)   Increases internal linking
2)   Eliminate redundant out-bound links
3)   Using the No-follow links

It occurs when links going out from an extract further link juice which otherwise should preferably be spread among the internally linked pages. This causes harmful effect on a site's PR and therefore, is a cause of concern to be dealt with effective measures in order to preserve the rank and prevent the loss.

do follow is really good to your site.