How do VoIP services, such as Skype and Yahoo, connect to landlines?
We have a server connected to a landline using asterisk, so I'm thinking this server will bridge our VoIP conversation and connect it to a landline.
But if this is the case, wouldn't Skype need a lot of servers placed around the whole world just to connect to landlines?
Yep. That's how telephony works. It's unlikely that Skype runs a bunch of servers themselves - they probably license the right to use a commercial telephony service, probably through the backbone carriers (just speculating).