Skype accounts blocked,why?

So many skype users have been blocked recently. If you are unlucky to be blocked, I think you would have a bad experience. It would spend long time for you to contact Skype customer support center. But you never know when it can be solved.

Why skype accounts blocked? Is there any rules or regulations published on skype website? I hope that I can find some tips from Skype Knowledgebase, but unfortunately I failed.
However I find something on Skype Coummity , Following is the standard reply of Skype moderator:

"Skype has blocked your account for your own safety e.g. someone hijacked your account and is using your credits or someone has stolen your bank details to buy credits or perhaps you accessed your account from a known illegal IP address or from a known fraudulent destination.Please file a support ticket here: Submit Request,If you don't receive a reply 4 BUSINESS days after filing your ticket advise here with your user name and the date you filed your ticket."

"Accounts get blocked for various reasons: calling or buying form a known fraudulent IP (different Internet connection, country, area), buying credits for two or more accounts with the same payment details (the system does not know the details have not been stolen by an unauthorized user), indeed stolen payment details, etc.
The anti fraud system is very tight and can be annyoing for the user though it is always for the safety of the user. The reason why it takes often a minimum of 4 days to unblock is the fact that the requested and forwarded account and payment details needs to be verified by third payment processors.
Unblocking is done manually."

Ok, here I would like to collect all possible factors that would make skype accounts blocked, if you know anything,please don't hesitate to tell me, I would post it here:

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>> One payment detail can only be used by one skype account.

For example, if more than 1 skype accounts (even thought all of the skype accounts are yours) use your same credit card to purchase skype credit, the skype accounts is possible to be blocked.
It is same as the paypal account,bank details,moneybookers and so on.

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>> You attempted a purchase using a different credit card or PayPal account from your usual one.

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>> Skype notice that your bank details,Credit card ...... has been stolen, or skype notice that someone hijacked your account and is using your credits . In the situation,Skype would block your account first.

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>> You purchase skype credit from third party, but the third party purchase or obtain the credit with illegal way. your account also will be blocked.
So you had better choose the website carefully when purchase credit.
Usually you can visit skype official site to purchase credit or order unlimited calling plan ,please visit here Ways to pay for Skype products .

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>> For skype accounts that subscribe unlimited calling plan , it is more easily to be blocked.
For example:
> If Skype notice an unusually high number of calls from your Skype account, your account usually would be blocked.
> Your IP address is changing often (based on the country you are in)
> You dial many different telephone numbers in short time
> You use proxy to login skype

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