To add on the epic posts made by D-Man and others. I fail to see why people complain so much when there has been past examples of multiple title changes back in the day and people never complain about them now as much as they do with today.
Example One:
Survivor Series 98-Wrestlemania XV
The World Title has been vacated and a new tournament starts which ends up with Rock winning the belt. Between SS98 and the Raw following the St. Valentine's Day Massacre, the belt changed hands 5 times between The Rock and Mankind and eventually a 6th exchange went to Austin. That's 6 changes in the space of about 4 months between 3 guys and it was greatly booked for the story, it wasn't about the title, it was about the rivalry and the belt played a role there.
Example Two:
Backlash 2000-Fully Loaded 2000
This is the prime example of what the Cena/Orton feud emulates, the rivalry of Rock and Triple H in 2000. In the space of 4 months they exchanged the belt 3 times over 3 PPVs because both men were booked to be as strong as the other, they had wins over each other and neither lost momentum from dropping the belt. Ironically this had an Iron Man match involved in the mix of things and the feud didn't even finish, they still had two matches further on afterwards. But this is how Cena and Orton are being booked, they're getting a rub off of each other that it's not about the title, it's saying that these two are THE men of the company and we will remind you that we can have each of them lose per month to show these two are the best and neither is going to lose momentum having been through I Quit Matches, Hell in a Cell and now an Iron Match Match
Example 3:
Wrestlemania X8-Summerslam 2002
Ok this one saw the most title changes between 6 people in less than 6 months. In this order Jericho-Triple H-Hulk Hogan-Undertaker-The Rock-Brock Lesnar, they all head the Undisputed Championship and with the exception of Undertaker during this period (excluding Jericho and Lesnar as they were the end/start of their reigns), no one held the belt for more than a month. Why? Because they had to adjust to the ratings going up and down, the unpredictability gave WWE a spark to keep watching as a new champion could come at any given moment. Much like WWE of today, they need the ratings to come in, so giving new championship reigns helps them find who brings in the figures they need, which is why the belts are changing hands.
It's trial and error as it rightly put, which has been this year for WWE, they're testing the waters for what the future has right now and so far WWE is getting the responses they want. Like it or hate, this is how it's always worked, title changes brings in reasons to talk, it's exciting and brings unpredictability, much like the Iron Match. We don't know how that one is going to pan out, Cena MAY end up on Smackdown, Cena MAY win the title, it's unpredictable and most importantly, the kids love it!