I suggest using a2a for those people you'd really like to chat with on a friendly basis. This can be different for everyone, but people who live near you, or live somewhere you are interested in, or connect with the same ECAs, or whose forum posts intrigue you are some examples of who to select. I take a2a has a supplemental social enrichment aid and use it casually, like 'off-the-record' regular emails. It seems less intrusive than using someone's personal email.
