In the US, clothes dryers are one of the leading causes of house fires:
In 1998, CPSC estimates that there were approximately 15,600 clothes dryer fires resulting in 20 deaths, 370 injuries and $75.4 million in property damage.
In 2010, an estimated 16,800 reported U.S. non-confined or confined home structure fires involving clothes dryers or washing machines resulted in 51 civilian deaths, 380 civilian injuries and $236 million in direct property damage. Clothes dryers accounted for 92% of the fires; washing machines 4%, and washer and dryer combinations accounted for 4%.
A fairly comprehensive study about lint ignition was completed by the Consumer Protection Safety Commission (CPSC) in 2003. This study showed that the dryer's internal temperature greatly increased once the vent pipe's area was reduced by 50%. In homes, this reduction is due to lint gathering in the pipe.
This manual for a random dryer mentions that minimum air flow through the 4" (10 cm) diameter vent pipe is 1,200 feet per minute (20 ft/s or 6.1 m/s).
There is a concept of minimum velocity in drainage pipes and culverts to ensure that they are self cleaning, i.e. debris does not build up.
Obviously air and lint are different than water and sediment. I haven't been able to find any particle properties for lint.
Is the solution to lint clogging dryer vents just to increase the velocity of the air in the vent?