Here are some interesting links.

HP obtained a patented backdoor system in 2008 (filed mid 2000 and approved around the start of 2001).

https://www.google.com/patents/EP1059578A2

Certicom (the same company DUAL_EC was filed under) has a new key escrow system patented.

https://www.google.com/patents/EP2637350A2

Key escrow system filed in 2004 and published in 2011:

https://www.google.com/patents/US8015597

2008-2012 stateless key escrow patent:

https://www.google.com/patents/US8315395

"Automatic recovery of TPM keys" - Lenovo

https://www.google.com/patents/US8290164

Oops, here's a Microsoft "cloud storage" key escrow system from 2011-2012.

"Some of the files stored on the network server may be sensitive or confidential. The user may wish to restrict access to those files. The files may then be encrypted or otherwise protected with a password or other key. The user may not trust the network server to store the key, and may thus desire to retain sole possession of the key. Such users, however, often lose (or forget) their passwords or keys. Moreover, other third party users may legitimately require access to the stored, encrypted files."

"FIG. 3 illustrates a flowchart of an example method for providing third party data access to a user's encrypted data according to a predefined policy."

"In some cases, however, while the data storage system is not able to decrypt the user's data, it may be necessary for an outside entity (e.g. a governmental entity) to access the user's data."

"In cases where the encrypted data is a cryptographic key, that key may be stored as a plurality of shares. The shares are mathematical transformations of the user's private key, and each share is provided to one of the verified third parties. Each verified third party publishes his or her own public keys, and encrypts his or her share of the encrypted key using their published public key. The verified third party shares encrypted according to the third partys' public keys are then stored in the data storage system. Because the shares are encrypted according to the verified third parties' public/private key pair, the data storage system is prevented from accessing the encrypted shares, and is further prevented from accessing the user's data."

"In some cases, the user's data may comprise, at least in part, a cryptographic key. The user's data, including the key, may be stored in multiple different shares."

Encrypted data AND keys!

The patent examiner cited "The Risks of Key Recovery, Key Escrow, and Trusted Third-Party Encryption" when doing his examination.

https://www.google.com/patents/US20120321086

http://academiccommons.columbia.edu/catalog/ac:127127

Some Raytheon for good measure. A bit older, but certainly Bush era.

https://www.google.com/patents/US7269261

Motorola [1]. Certicom [2]. Honeywell [3]. Motorola [4]. Deutsche Telekom Ag [5]. IBM [6]. Apple [7]. ‎Fujitsu [8]. Red hat [9]. F-Secure [10]. Sony [11]. Seagate [12]. Dell [13]. Sprint [14]. Nokia [15]. Gemalto [16]. Intel [17]. Samsung [18]. Symantec [19]. Sun Microsystems [20]. Toshiba [21]. Cinea [22]. General Dynamics [23]. Citicorp [24]. Siemens [25]. Ericsson [26]. VMWare [27]. Facebook [28]. HP [29]. Cisco [30]. Liquid Machines [31]. GIC [32]. Microsoft [33]. Novell [34].

And of course the US patent system has a classification for key escrow systems: 380/286.

http://www.uspto.gov/web/patents/classification/uspc380/defs...

[1] https://www.google.com/patents/US7116786

[2] https://www.google.com/patents/US8688998

[3] https://www.google.com/patents/US20070140496

[4] https://www.google.com/patents/US5241597

[5] https://www.google.com/patents/US7162037

[6] https://www.google.com/patents/US8195959 & https://www.google.com/patents/US7856664 & https://www.google.com/patents/US7873170

[7] https://www.google.com/patents/US20090319769

[8] https://www.google.com/patents/US6754349 & https://www.google.com/patents/US8055911 & https://www.google.com/patents/US7752318

[9] https://www.google.com/patents/US8144876 & https://www.google.com/patents/US8494169 & https://www.google.com/patents/US20070280483

[10] https://www.google.com/patents/US8824682

[11] https://www.google.com/patents/US7672458

[12] https://www.google.com/patents/US7899186

[13] https://www.google.com/patents/US20090080663

[14] https://www.google.com/patents/US7869602

[15] https://www.google.com/patents/US8107623

[16] https://www.google.com/patents/US8074076

[17] https://www.google.com/patents/US6950523

[18] https://www.google.com/patents/US8315386 & https://www.google.com/patents/US20070172069 & https://www.google.com/patents/US7492895

[19] https://www.google.com/patents/US8397281

[20] https://www.google.com/patents/US7050589 & https://www.google.com/patents/US7660423 & https://www.google.com/patents/US20100142713

[21] https://www.google.com/patents/US8099609

[22] https://www.google.com/patents/US7277544

[23] https://www.google.com/patents/US20070195960

[24] https://www.google.com/patents/US6970836

[25] https://www.google.com/patents/US7313697

[26] https://www.google.com/patents/US20080152151

[27] https://www.google.com/patents/US8234518

[28] https://www.google.com/patents/US8490166

[29] https://www.google.com/patents/US6577735

[30] https://www.google.com/patents/US8631227

[31] https://www.google.com/patents/US7796760

[32] https://www.google.com/patents/US20040052380

[33] https://www.google.com/patents/US20070003065

[34] https://www.google.com/patents/US8098828