Please be careful before you pay and read:

          https://bitcointalk.org/index.php?topic=362108.0

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UPDATE DEC 11: WARNING: GROUPHASHING IS A SCAM
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Hi All,

Yesterday, I ordered a 2 MH/s contract for 2.10000 BTC with Grouphashing.com.

Now, I am getting a little bit worried when I read:
    http://bitcointalk.org/index.php?topic=345187.0
    http://bitcointalk.org/index.php?topic=335963.0

On their website: https://grouphashing.com/privacy_policy , the following address is mentioned.
    Zilverenberg 36, 5234GM, 's-Hertogenbosch, Netherlands, grouphashing@gmail.com

When I search, I do find some companies on this address (but no grouphashing?):
  http://www.oozo.nl/?acid=&q=Zilverenberg%2036,%20den%20bosch
I did contact Peritus Consult, but they are not affiliated.

When I check the domain, I get the info below.

http://who.godaddy.com/whoischeck.aspx?domain=GROUPHASHING.COM
Registrant Name: Registration Private
Registrant Organization: Domains By Proxy, LLC
Registrant Street: DomainsByProxy.com
Registrant Email: GROUPHASHING.COM@domainsbyproxy.com
https://www.domainsbyproxy.com/AboutUs.aspx

=> My question is: does anybody have good experience with this company ??

@GroupHashing ( https://bitcointalk.org/index.php?action=profile;u=156017 )
Can you please respond to this?