Do ya do it or not?
I do, cuz I prewash everything, new or 2nd hand, but I find FQ's don't seem to come out very square. It is cuz they're cheap? or do all FQs lose their shape?

I prewash. I work too hard on my quilts to not prewash them...they do shrink and bleed. I do not prewash my batting so I still get a nice crinkle look.

I am a pre-washer so I put my FQs in a bag and wash/dry as usual. I know of people who wash them by hand.

Depends on material

since all woven fabrics (if they shrink) will shrink more in one direction than the other it is normal for fabric to be a bit (mis-shaped) after washing/drying. many people who choose to pre=wash pre-cuts find this happening- it can be quite bad with 5" charm squares-
when pre-washing yardage you simply don't notice it as much it is not as big a deal....that's why if you contact the fabric manufacturers and ask they will tell you they do not recommend pre-washing any pre-cuts- they say they are meant to be used as they are- pre=washing is not necessary ...
they simply do not understand that (some of us) always pre-wash- regardless---
so we have to live with the results of our (not-recommended) decision.
one of the big reasons i seldom spend my hard earned $$ on pre-cuts...the frustration (and waste) seems to outweigh the convienience for me....i'd rather cut my own pre-cuts after pre-washing- that way i know my 2 1/2" strips are going to be 2 1/2"...and my fq's are going to be 18"x20"

Did it once. Threads everywhere. What a mess!

I rarely prewash anything; use a colour catcher in the first couple of quilt washes.
If I feel I need to wash FQs I do it by hand in the sink. They're too distorted by machine washing, even in a lingere (bad spelling) bag

I am also a prewasher. Have had too many fabrics bleed like stuck pigs. Fat quarters and fabrics from BOM's get a quick rinse with hot water. If the piece is really small, I'll even iron it dry instead of using the dryer. I care more about not ruining my finished product, than losing an inch of fabric.

I only prewash yardage. Use color catcher.

fabric bleeds.. absolutely !!! small stuff, I use .. OK.. will get a lot of flack from this.. but really does test the fabric.

Dawn dish soap in a 6 cup glass measuring cup under the facet.. in hot water..

really does test the fabric and can see right away if it will be a problem.. some just washes out.. and clear water then is what comes after the soap is gone..

I don't want to chance some fabric running color.. too much work !

Larger sizes, I wash normally, and dry normally.