The better you know the people who will receive your memo and the less important the rank  of the person/people the more you can use incomplete sentences and abbreviations.

Please bear in mind that this memo might be forwarded and filed.

While being short, you still need to keep an eye on the overall tone that it will create and also that the message is still clear for everyone. Now as well as in any time from now, when the context is no longer so easy to get.