Whenever I put jeans in the dryer, it is intentional, and usually with bad results, so I have stopped doing it all together. If a tailor refused to hem without a toss in the dryer, I would just lie and say I did. The reason tailors prefer you to dry is so that you don't come back and complain later that they are too short and try to blame it on them.
It depends what you normally do. If you normally put your jeans in the dryer and never have any problems with tightening or bagging, then go for it. Or if you anticipate that they will eventually get tossed in, you may as well. But for me, I would rather just TELL my family members/roommates not to do it and that has always resolved the issue with no further problems. I guess I'm lucky that my family always asks, or just puts my clothes in the dryer without turning it on. I would NEVER put someone else's clothes in the dryer without asking them first. I would CRY if someone did that to me! The only clothes I ever put in the dryer are loungewear, cotton underwear, and PJ's...everything else would be ruined.
