Personal pronouns (like I, we, and you) are important in letters and memos. In such documents, it is perfectly appropriate to refer to yourself as I and to the reader as you. Be careful, however, when you use the pronoun we in a business letter that is written on company stationery, since it commits your company to what you have written. When stating your opinion, use I; when presenting company policy, use we.
Nobody liked your project idea, so we are not going to give you any funding. The first version is a weaker statement, emphasizing facts not directly relevant to its point. The second version provides the information in a simple and direct manner. But you don’t need to be an expert on style to know that the first phrasing is diplomatic and respectful (even though it’s less concise) as compared with the second version, which is unnecessarily harsh and likely to provoke a negative reaction.