This predates Google Talk and is rather about the XMPP Gmail integration. Back then XMPP was the hot topic in tech circles (Twitter was even prototyped to be XMPP based) and people were switching to it and recommending it to others to replace ICQ/MSN/AIM etc. However, often they recommended others to use the Google XMPP service as back then Google was still naively seen as the "Do no evil" good guy, having just started up recently and giving away free things like previously unheared off 1GB of email storage etc.

So the situation is not quite comparable to AP and Facebook (and XMPP is far from dead), but it is still possible to draw some lessons from it.