http://reports.internic.net/cgi/whois?whois_nic=google.com&t...
That said I think appeal to authority is quite useful in this situation.
But I would have said the same about mit.edu and they got reassigned about a year ago. Obviously not for long, but the damage someone well-prepared could do by owning google.com for just 30 minutes is scary.
I think the idea behind these services is, they're not just a registrar. Broadly speaking, their business is "know your customer". They're boutiques. They protect large companies against the vagaries of DNS hacks, expired domain registrations, typosquatting, etc.
E.g. a (long) while ago Microsoft failed to renew hotmail.co.uk, just like they previously forgot to renew passport.com. But today, Microsoft can't forget to renew microsoft.com, because that's now MarkMonitor's job. Similarly, renewing passport.com is now the job of (according to whois '=passport.com'):
Corporation Service Company(c) (CSC)
The Trusted Partner
of More than 50% of the 100 Best Global Brands.
The bad part is if CSC screws up, quite a few companies could be in a world of hurt.This is different than a registrar lock in that a registrar lock is managed by the registrar (GoDaddy, Tucows, etc) but a registry lock is managed by the registry themselves. It requires personal contact with specific individuals to enable and disable the lock, making attempts to steal domains more difficult (but not impossible since social engineering is still feasible).
I've never used MarkMonitor before, but I did handle the registration for a hugely popular domain at one time. They decided to move to MarkMonitor but in the meantime they requested a registry lock set up on their main domain. This turned out to be very good idea since the registrar at the time was social engineered into changing the credentials for the account (with forged letter head similar to the fastmail.fm attack). The attackers were able to change the nameservers for little used domains but their main domain could not be modified.