101domain are complete scammers. A few friends of mine wanted to get a .so domain when they went to auction this past April. 101domain didn't even bother to go to auction... but did try to take their money.
I just got the email myself, it appears that payment information was accessed so they are telling their customers to check the account of the card used, they did not inform users of retention of payment information nor does it look like they used a proxy service, so it appears that they where storing original card numbers on their systems. Fortunately, I use a specific card for online purchase so I will just cancel the card and ask for a new one. I am not real happy about having to go back through transactions and look for fraudulent activity, though.
PayPal is linked to a checking account usually, so I don't see how that's safe. I use one and only one Amex for all online purchases. If anything goes wrong, cancel the one card...start over.
For 101domain there's a simple reason: For some exotic country TLDs they are the only provider that even has a web interface (seriously).
Apart from that: Avoid them when you can. I have a couple domains there and the experience is terrible. Inquiry roundtrip times are measured in weeks...
I used it because it was by far the cheapest domain reg that had built in Trustee services. I pay them $8 or so and then I can register a domain anywhere in the world. In my case, .it is limited to Italian residents.
https://www.google.com/search?q=site%3Ahosted.verticalrespon...