I've heard this alot... I'm not sure how Beardedragon has never heard it but who knows. The biggest substrate/impaction risk I hear about is keeping reptiles on sand, but I have also heard about aspen, cocoa fibre, even the recycled paper I use as impaction risks. I've never really bought into it; if they can digest bones, a little bit of paper is probably not going to ravage their digestive tract...
Never had a problem personally, but I've only had the BP's for a year. Kingsnake on coconut fibre for... 7 years? 7 or 8... And again, no issues, and she has definately eaten her fair share of it (stuff sticks to a wet mouse like crap on velcro...)
Also never seen a substrate-induced impaction in my 3 years at a major pet store, even with the animals on sand... So...
Edit: Just wanted to thank you, Skiploder, for making these posts. So... Thanks!
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