We've posted many articles discussing misleading applications and the tricks and techniques that are used to get them onto a user’s computer. Typical techniques employed include repeated, often aggressive, warnings about serious computer problems such as malware infections and system errors. Typically these warnings are fake and are used to scare the user into parting with their money in order to correct the "problems".
You can read the rest of this Blog here: Technical Support Phone Scams.
[edit: Fixed posting error.]