WSJ.com - Google to Introduce Instant Messaging: "In instant text messaging, America Online is far and away the leader. In July, AOL had 41.6 million average active users from its various services -- the most well known of which is AOL Instant Messenger -- according to comScore Networks, a market-research firm. Yahoo's competing service had 19.1 million users, while Microsoft's MSN Messenger had 14.1 million users last month, according to comScore.
AOL declined to comment on Google's service. A Yahoo spokeswoman said it welcomes newcomers to a market where it 'has consistently taken share from competitors.' Microsoft, which has 170 million instant-message users world-wide, continues to invest in its communications products and build stronger relationships with its users, a Microsoft spokesman said."