Questions

Well, all those means are good for certain types of communications:
Notes are very handy when you are working in NUZ and have a sudden thought or a message for Netcells, for example, when refining your site. They are transient, non-urgent communication and can be recycled.
SecureMessage is, by definition, good for important, confidential data (delete it after reading if you wish). SecureMessages are very useful for people who get a lot of email - they are completely spam-proof and you can use them for really important communications, unless you overwrite them, your messages will still be there in 2 years time - whatever happens to your local computer in the meanwhile.