That would be because Carbie Cleaner is 20-30% Acetone, and 35-45% Toulene, and 20-30% Methanol.... and its Acetone that does all the work anyway... I personally, would not like to handle/inhale Toulene and Methanol on any regular basis.
Acetone is naturally produced in the body, and disposed of from the body in normal metabolic process. Diabetics actually produce it in quite large amounts... as do Pregnant women and nursing mothers...
Toulene on the other hand, produces anti-depressant-like effects in tested animals, and is a blocker and antagonist for various receptors in the body. Theres a reason its abused as an inhalant 
Methanol is also highly toxic, although you need to be ingesting pure methanol to make it relevant.
So yeah.. the new technique.. is just using a pressurised can version of the 'old' technique that also used only the primary active ingredient anyway (Acetone...) and the new technique is far worse for your health...
The MSDS for one of the more popular Carbie Cleaners out there (at least here in Australia) : http://www.crcindustries.com/faxdocs/msds/5079.pdf
Personally, I'd rather stick to the purer 'traditional' method... Or you could dable with using acetone in a 'spritzer' bottle to achieve the same effect.... without the Toulene or Methanol (which don't help the process, just makes it far more unhealthy....).
MSDS's are always worth checking too before launching into experiments... you can for example create deadly gases (we are talking less than 1 part per 1000000 is lethal...) from PVC without very much effort at all....
