how safe are stretched tires?

[Eurolook71]

Hey, you know that sick look all the euro folks give to newer watercooled dubs? You see them in the really expensive euro mags at barnes and nobles. Any way, all the tires ride on like 16 (and typically much smaller) diameter, with like 7, 8, and ever 9 wides, and thats on the front end! I know that a wider rims doesnt mean more peformance, and can even stress out the suspension, but how "safe" is a tires that has the bead just begging to be pulled of the lip?? I wouldnt go any wider than 7 on my super, but with some deep dish rims (15X7, 38ET), and some slimmer struts, I think i would get the look I'm going for.