I always wash first in a lingerie bag or pillowcase. I've had several projects ruined by fabrics that bled. For example just this weekend I was prewashing fabric and several of them bled. And these aren't cheapo fabrics. One was a maroon, older Mumm fabric (from LQS not Joannes) and it got all over the pillowcase. I also had some batik type fabric run this weekend. Had I put those in a quilt I would have been very upset. Yes, the raveling can be a pain, but it hurts worse to lose a project you've been working on for weeks or months. In my book it's better to be safe than sorry.
When I need the fabric, I iron it and starch it. Feels just like brand new again but it won't run! I agree most fabrics from Quilt stores don't bleed. But it's that 1-5% that are killers: