When you apply for an EIN they ask for a responsible parties SSN. I have applied for many EINS for clients and everytime I have had to input someone's SSN.
From the IRS website....
All EIN applications (mail, fax, phone, electronic) must disclose the name and Taxpayer Identification Number (SSN, ITIN, or EIN) of the true principal officer, general partner, grantor, owner or trustor. This individual or entity, which the IRS will call the “responsible party,” controls, manages, or directs the applicant entity and the disposition of its funds and assets. If there is more than one responsible party, the entity may list whichever party the entity wants the IRS to recognize as the responsible party.
According to the Instructions for the current revision of the application, the “responsible party” is defined as follows:
For entities with shares or interests traded on a public exchange, or which are registered with the Securities and Exchange Commission, “responsible party” is (a) the principal officer, if the business is a corporation, (b) a general partner, if a partnership, (c) the owner of an entity that is disregarded as separate from its owner (disregarded entities owned by a corporation enter the corporation’s name and EIN), or (d) a grantor, owner, or trustor if a trust.
For all other entities, “responsible party” is the person who has a level of control over, or entitlement to, the funds or assets in the entity that, as a practical matter, enables the individual, directly or indirectly, to control, manage or direct the entity and the disposition of its funds and assets. The ability to fund the entity or the entitlement to the property of the entity alone, however, without any corresponding authority to control, manage, or direct the entity (such as in the case of a minor child beneficiary), does not cause the individual to be a responsible party.