In the ABA Journal, the incomparable Bryan Garner has an indispensable list of words and phrases that lawyers should not use: herein, deem, know all men by these presents, provided that, pursuant to, said, and same. And "and/or." The only one that I am occasionally guilty of is "and/or" which in the odd circumstance just seems to me to be more efficient than ", or both." Garner musters some pretty persuasive authority against "and/or"
American and British courts have held that and/or is not part of the English language. The Illinois Appellate Court called it a "freakish fad" and an "accuracy-destroying symbol." The New Mexico Supreme Court declared it a "meaningless symbol." The Wisconsin Supreme Court denounced it as "that befuddling, nameless thing, that Janus-faced verbal monstrosity." More recently, the Supreme Court of Kentucky called it a "much-condemned conjunctive-disjunctive crutch of sloppy thinkers."
Damning to be sure, but I'm not sure I buy Garner's argument for why and/or is never appropriate:
If a sign says "No food or drink allowed," nobody would argue that it's OK to have both. (Or includes and.) And if a sign says "No admission for lawyers and law students," would you argue that either could go in alone? You'd be thrown out of court.
The real problem with and/or is that it plays into the hands of a bad-faith reader. Which one is favorable? And or or? The bad-faith reader can pick whatever reading seems favorable.
Here's an example that makes Garner's point from a recent Nebraska Supreme Court opinion (they didn't get the memo from Kentucky):
On reinstatement to practice by the Supreme Court, such party shall, on written request and upon payment of the requisite fees and/or mandatory assessments, be restored to membership in this Association.
But what about this subheading?:
Budget Impact -- Moderate state and/or local costs, likely partially offset by the avoidance of federal penalties.
The subheading prefaces an explantion that, depending upon implementation, a particular activity could incur state costs but not local costs, local costs but not state costs, or state and local costs. A simple "and" just doesn't cut it.