One of the move overused words (or is it two words?) is "and/or". Somehow, using it has become a bit of an obsession, with people putting it in anywhere they think possible. This is not always a good thing --- not only does it sound clumsy, but it can occasionally obscure more than it reveals.
Take, for example, this piece of text, from the website of a large Australian bookstore that also sells computers.
Quantity limits apply: one desktop and/or one notebook per academic year.
Is one allowed to buy (a) one desktop and one notebook, for a total of two items; or, (b) one desktop or one notebook, for a total of one item? Either the "and" or the "or" is unnecessary and incorrect, but (short of telepathy) it's impossible to say which one.
The moral of the story is: make sure you're clear on the meaning of your sentence before shoving in an "and/or"!