Fifty Shades of Grey is a terribly written, (inexplicably) terribly popular book series, originally created as fanfiction for a series that featured sparkly vampires.
I myself have a few scarves (and ties and jumpers and even a sock) that have been relegated to the graveyard of items of clothing stretched beyond recognition from being used as a certain type of restraint, so I understand the appeal. But the relationship and type of sex shown in Fifty Shades of Grey are not healthy, nor properly consenting, nor proper BDSM.
BDSM is an overlapping acronym for bondage and discipline, dominance and submission, sadism and masochism. And while EL James gets some things in her barely-more-than-vanilla-sex book right, others she gets dangerously wrong (all the while mutilating the English language).
Restraints she gets right: Christian Grey (or should I say Edward Cullen?) uses his impressive array of suit ties to hold insert-generic-shy-awkward-white-teen-novel-protagonist-here in place instead of anything hard. While I may have invested in a pair of pink fluffy handcuffs or two in my time, I would strongly recommend sticking to fabrics. They’re easier on the wrist, you can make them as tight or as loose as you want, change the position of hands or feet or whatever — and if things go wrong, they are easier to cut off than trying to wrench metal around.
Although EL James mentions safe words, I’m fairly sure I noticed examples where safe words were ignored. This is not okay. If the safe word gets said, stop. No coercing, no begging, whining, pleading or sulking. Stop instantly, without complaint.
Also stalking is not okay in any relationship. Having a BDSM relationship with someone does not mean abuse is okay. Abuse is never okay, even if you do enjoy engaging in hot BDSM sex.
If this type of relationship fascinates you, do your research. Do NOT model a relationship on Fifty Shades of Grey. In fact, take it as a “What Not to Do” guide. And invest in a few fabric items that can be your designated restraints; too many a scarf has been lost to hot sex already.