Does your charity have a communication strategy? Do you ensure that one person will not receive two (or more) letters from your organisation on the same day (and maybe even from different departments)? Do you respond in the way your donors/contacts want you to? Do you let supporters opt-in to just the information they want to receive?
If not, then it's probably time you did.
Whether you run multiple database systems (and by that I mean databases, spreadsheets, email lists and all the rest) or you have a single, centralised database, either way this applies to you. If you have multiple systems then you must ensure that individual staff members cannot simply decide off their own back that they are going to do a mail-shot from their system, and if you have a single database, then although you will be able to enforce some control, you could have just as many problems with individual users demanding to use the data for their marketing and communications.
If you don't control this then your supporters and donors will get annoyed and that isn't going to help you at all.
Do consider if you can offer your contacts the opportunity to opt-in to just what they want to receive and hear about. E.g. specific events/types of event, fundraising requests, volunteering opportunities, generic newsletters, emergency appeals and so on. And how - email, letter, telephone. It can be quite a scary thought that you will no longer be able to contact everyone about everything but it will work better for you. You will be targeting your supporters better and more appropriately, you will lower your costs, you should get better response rates, you should get happier supporters and you will be working more efficiently.
Communication is at the heart of all good relationships – including yours and your supporters.