I'm thinking along similar lines. There was a thread a couple of days ago that seemd to indicate that sealing was the problem, and used tyres might be too loose to seal properly without an industrial compressor.
with tubes, i get about 1 puncture every 2 months (none in 2 weeks in the alps).
i try to run Ghetto on my Dh bike (both wheels mavic 721 and 2.5 highrollers), but for the moment have given up.
a) i found wheels would randomly deflate over night (no cause found), i guess this would be about 1 per fortnight.
b) i never heard any burps, but would finish a rocky Dh run with softer tyres than i started with, and a good coating of sealant all over my back / legs / bike / bag. on a longish run (10mins) enough air would leak out to cause a failure (loss of seal, goo everywhere, friends falling over laughing uncontrollably).
Ghetto ISN'T a weight saver compared to normal xc tubes – which weigh 200g, you replace one of those with about 100g of bmx innertube, and 100g of sealant.
Ghetto does offer a 200g saving per wheel compared to Dh tubes (400g), and so i'm prepared to give it another chance or 2.