Let the file ~/.emacs.d/recentf contain a tramp-sensitive entry,
e.g. let it consist of the following:

--8<---------------cut here---------------start------------->8---
;;; Automatically generated by ‘recentf’ on Sat Mar 25 11:51:22 2017.

(setq recentf-list
      '(
        "/su:root@rosalinde:/etc/"
        ))

(setq recentf-filter-changer-current 'nil)


;; Local Variables:
;; coding: utf-8-emacs
;; End:
--8<---------------cut here---------------end--------------->8---

and let ~/.emacs consist of this line:
(recentf-mode 1)
Alternatively, customize the variable recentf-mode to t and save this
setting.

Now starting emacs raises the error "Variable binding depth exceeds
max-specpdl-size" and recentf-mode is not enabled.  Starting emacs with
--debug-init produces the attached backtrace.

(With the above recentf file, starting emacs with `-Q --eval
"(recentf-mode 1)"' or with `-Q --eval "(custom-set-variables
'(recentf-mode t))"' does not raise an error but prompts for the
password for the file "/su:root@rosalinde:/etc/".)


In GNU Emacs 26.0.50 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.20.10)
 of 2017-03-24 built on rosalinde
Repository revision: 4fbd330fae54a9c45d4a717127aa86d75e9938d5
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description:	openSUSE Leap 42.2