Setting aside specific products (i.e. porn), the answer is still yes.
The first and biggest example is pull-list discounts. Lots of stores offer, and lots of customers *expect* to get a discount for opening a hold. And it's easy to see the logic behind that. "I am telling you upfront what you should buy. This is a no-risk sale. I should get a discount for that." To an extent, that is truth in that. But it's not 100% accurate and is the source of many of comic store's trouble. First off, discounts have an exaggerated impact on profit margins. If I give you a 10% discount, that is a 20% or more hit to profits. Depending on volume, most comic stores get their product for ≈50% of cover. So if I paid $1.50 for a comic that has a MSRP of $3, and I give you a $0.30 discount, I made 20% less. And my other expenses (labor, rent, utilities, etc.) haven't dropped either. But it would still be worth if for some customers if it wasn't for certain behaviors - namely pull abandonment and selective purchasing - causing problems.
Pull abandonment is exactly what it sounds like. For one reason or another a customer would just stop coming in to pick up their comics and also would not tell us. We (potentially) end up buying a lot of stock, not even putting it on the shelf, and then take a loss on it. [Comics have a fairly short new shelf life. Something six month's old is in the back issues boxes and not worth cover.] There are solutions to this problems but they come with their own issues. First, we tried not putting stuff in full holds. In other words, if you haven't picked up your hold for a week (or a month, or whatever), we stop putting stuff in. Problem is a lot of comic customers are NOT weekly purchasers. I know this will shock some of you that drop by every week (and we had lots of those customers) but a lot of customers would come in once a month or so. It's one of the whole points of having a pull list. You know you'll get the comics you want. And if we stopped filling someone's hold if they took a little too long in between visits (thanks to a summer vacation, or really busy school quarter, or something), then the customer would be upset. So we had a risk to manage and failure ate up our profit margin. The second solution was to require a credit card be on hold against your pull list. That way, if someone abandoned their pull list, we could just charge the card. But that created it's own set of problems. People without credit cards or who didn't want to leave their billing information (understandably). Even if they left a card, card's expired or got changed. We would try to bill the card and it wouldn't go through. A few times, we would successfully bill the card and then the person who abandoned the pull list would dispute the charge and we would end up with that headache.
Selective purchasing is when someone would come in and look through their held comics and decide they really didn't like Green Lantern anymore so they didn't want it. Great. But I had to order three months ahead. So I have the next three Green Lanterns coming for you. And those are now a lost cost. Some customers would do this all the time - particularly ones who followed artists/writers and not characters. Or they would ask us to hold a new title, and then decide they didn't want it.
The worst was the combination guys. Guys who would come in once every two/three months and then go through and pick only the stuff they really wanted, leaving us with the rest of the stack. And THEN they wanted their discount...
The second biggest issue is related to the previous discussion about game stores as hangouts. It's great when you have a devoted customer base who likes to hang out at the store. They end up spending more money. But they also have a huge impact on the culture of your store. A group of five obnoxious teenagers who haven't figured out how to behave in front of girls, how to dress decent, etc. have a real negative impact on the store. And you can kick them out. But that has consequences and repercussions as well. And it's not just teenagers, a batch of grognard neckbeards (self included) change what a store feels like. So does a dozen crazy pre-teens playing Pokemon. Any group attracts like groups and drives away others. But they don't care about the negative consequences of driving others away. They expect you to cater to them, after all, we're spending a lot of time/money here. And truth be told, you may even like hanging with that group because they love things you love. But balancing that out with the costs was a constant act.
Finally, just expectations of hours. I almost always had to throw people at when it was time to close on the weekends. Sometimes customers would get upset about that.
 Please note this is not as much a problem on the game side. You pre-pay for a game item we have to order and I absolutely would give you a discount. That IS a no-risk sale AND I need to give you a reward for putting your money down and waiting to get what you want.
 An incomplete list: student graduated from school and moved on; lost job and they kept hoping to find a new job/come in and grab everything until they just gave up; got married and the SO was not down with spending anything on comics; just lost interest in comics; left on an LDS mission.