So, like all the best 'experts' out there, I'll give the 'final' answer!
OK, there's more to it, but it gets pretty complicated pretty quickly.
If life and the world is stable and everything is going great and you are considering cramming a tampon up your nose to stop the bleeding, I'd say 'nah, head to the ER or urgent care clinic'. There is some potential for harm, especially if you use a maxi instead of a tampon!
The risk from these things is low, but cram too aggressively and you could create new, worse problems. These products are 'clean' and not sterile. They are generally great for pretty superficial wounds in the short term, but for placing into non-standard openings, or for leaving in place more than the drive to the ER, there is risk. For example, a dry tampon up the nose will tamponade the bleeding. (Yup, that's the real word for stopping bleeding, now you know where 'tampon' comes from!) However, a dry tampon up the nose that is left in place for too long risks breaking down the nasal mucosa because it dries it out. To prevent this, the fancy $100 ER nasal tampons (or Rhino Rocket as we sometimes call them) are coated in vaseline. Yup, a tub of vaseline and tampons and you could change the world for pennies. (They make for great firestarters too, but that's another story for another day.) The vaseline keeps the mucosa from drying out too much and tearing while the bleeding stops, and it makes it a lot less miserable to remove.
Removal of these items is the other key point. I've removed some tampons that were in place for...I'll just say longer than intended. When used as directed, they generally don't cause problems since they are generally clean, used by healthy people, and left in place for hours, not weeks. However, if you have a dirty wound (fell on a muddy stick in the woods that went 2 inches into your thigh), the situation changes. If you're bleeding significantly from the wound, pack a tampon (or 2, 3, 4, however many to stop the bleeding) pronto and head to medical attention. A dirty wound that is packed and left alone for more than an hour or two is looking for trouble. In a really bad situation (no food for two days, dehydrated, no medical attention for miles), this situation becomes more critical as you were starting off with a depressed immune system and less reserve to deal with injury and subsequent infection. Personally, I'm going to consider the situation carefully. Flush the wound as much as you can with clean water and see if you can stop the bleeding with direct pressure outside the wound, maxi over the top, elevate the wound, etc. If that doesn't work pretty quick, flush it again, pack it and look for better care and antibiotics. If that wound stays packed as is for a day, when it is time to remove the dressing, you're risking rebleeding, tissue injury, a ton of 'discomfort', and recreating the badness that started this mess. If you are 'getting out of dodge' with one of these packed for a week with two tampons in your thigh held in place with duct tape...it just gets worse. If you can find good care, this is potentially very salvagable, potentially.
If we make the wound into the abdomen or chest cavity, the level of difficulty goes up, and the utility of tampons and maxis goes way down. You can't tamponade off a bleeder in the abdomen with a tampon. They work by expanding in size to block off the walls of the cavity and seal off the small bleeders while absorbing the fluids. If it is just absorbing fluid and not putting pressure into the space, add more tampons as needed, bigger wounds need more. In the belly, there is too much room for expansion that you'll never cut off the small bleeders, and too much fluid to work correctly. So we'll pray for no cavity wounds in the chest/abdomen/pelvis.
Maxis are great for external compression dressings since they are clean, absorbent, pre-packaged, and cheaper than a box of clean 4x4s usually. Off brand are generally ok too.
Clean the wound, elevate, direct pressure and good bandages will get you far. With some training these two devices (with vaseline) have a bunch of great first aid uses!
Good topic DestructoTex! And I know what you mean when you started the thread. Sometimes when things get awkward, like when it comes to tampons, you have to just jump right in and not worry about how messy it gets...no wait, that's not right either...