I don't really have a problem with the past contestants blogging, etc about the current show. I know many ex-Survivor people, people from TBL, people from Top Chef and Project Runway all do the same. They often have 'cast reunions' as well. I agree, I don't know how many of these people get time off or the cash to go, but I would suspect things aren't quite the same for them as they would be for us when they travel to places like Las Vegas. The show may cover some of the costs, the hotel might as well in order to 'advertise' that these people are there, etc. Plus, often when you're young and single and working (as most of them are) you have a more disposable income than say a married parent would.
One thing to note as well, there have been some successful relationships coming out of these reunions, so I often wonder if that's a motivation to many. Plus, the ones that truly haven't had enough of the 'fame' are indeed auditioning for BP.