It's important to note a congregation's thank you committee should spread their communication efforts across phone calls, mail, email and social media, when welcoming and thanking a new church attendee.
Using social media poses a more relaxed, inviting situation to speak to a newcomer and for the person to respond. Social sites like Facebook offers an opportunity to connect a new visitor with other church goers of similar taste and interests. And when someone posts an event or group outing in relation to the church, the new attendee will become aware of the organization's activities and may be more inclined to participate.
Read more HERE about incorporating social media in church communications.