I have invited 977 contact to google chat in 10 minute by smart work.
Here is the procedure to do it in smart way, Go to gmail web interface.
click on contacts,
Search for 'gmail.com'
Now you will get list of all contact who have gmail.com in it
Click on 'select all'
create group - name it 'allgmail'
now to compose mail,
type 'allgmail' and enter
you will fine that all the contact who has gmail.com is listed in TO: field.
now copy all these contact. Open gedit.
paste it gedit and save file as a.txtnow apply this command.
cat a.txt | sed -e 's/,/,\n/g' | sed -e 's/".*"//g' | grep -i @gmail.com > b.txt
This fill filter out unwanted character from a.txt and save into b.txt.Now open b.txt. you will find all contacts who have @gmail.com in ityou might not be able to invite all contacts at once.. for example when I was trying all 977 contact at once , I was getting error. So I invited 100 contact at a time. for inviting, click on 'add contact' at the bottom of Chat list.
Hope this will help in migration.INVITE ALL GMAIL CONTACTS to GOOGLE CHAT.