A few months ago United and Marriott anounced a partnership whereby anyone with United Gold, Platinum, or 1K status could immediately match to Marriott Gold status, which normally requires 50 nights in a year.
Separately, Hyatt has for a while offered Diamond status challenges to those with top-elite status on a competing hotel chain, granting Diamond status for 60 days which could be kept for the next calendar year if completing 12 Hyatt nights over those 60 days.
The kicker is that Hyatt considers Marriott Gold to be a matchable status. This means that anyone with United Gold or higher status can do a status challenge to Hyatt Diamond for 60 days. There are some reports that you may need to have one or two stays in Marriott for this. I personally had three stays at the time of requesting a challenge, and it was granted without an issue.
Even if you have no intention of actually completing the challenge, it might be worth doing this if you've got some Hyatt stays over the next 60 days which would benefit from having Diamond Status. I personally had four Hyatt nights booked on business already, and decided to spring for another eight over the course of my nomading (where for many nights I'd need a hotel anyways) to secure Hyatt Diamond status throughout 2014.
The fact that anyone with United Gold or above can do this opens it up to far more people than may be presumed.