Worthy is right. Most will have it somewhere, disturbing asbestos is when you have a problem. So, I'll qualify my advice by saying, "if you are thinking of removing it", and you find asbestos everywhere, then I'd probably walk away. As for covering it up, I guess it comes back to whether or not you'd fracture the asbestos fibers in the process of installing something over it. Maybe someone else here can give you good advice about that. I only base my opinion on the fact that we had an asbestos backed vinyl kitchen floor and a few heating system ducts covered in asbestos laden material (one was 80%) removed professionally and it cost about $5,000. Everyone will have their own choices to make with this stuff. One could argue we were overly cautious, and we probably could have removed the flooring safely enough ourselves, but we weren't at all comfortable removing the covered ducts ourselves. It just galled me to spend $5,000 to remove something and "get" nothing for it when I was spending a huge amount of money renovating the kitchen. (I realize maybe I "got" a healthier future! LOL). Anyway... stepping off my soapbox... somebody else?

I removed all the popcorn ceilings in my entire house with a garden sray tank, water, and a scraper. The process was spaying water and letting it sit, spray more water and when it's really loose scrape it off with a wide scraper. Skim with dry wall mud, sand (should only have to hit it a little with the dry wall sanding paper) prime, and paint. It's hard hard work but makes all the difference in the world. Popcorn ceilings should be illegal. Getting rid of them made my ceilings look a foot higher.

It's really tough to say how much asbestos it takes since some are exposed for a short time and get mesothelioma very quickly and at a young age. Others like my FIL are exposed daily at work for 40 years or more and don't get it until 50 years after first exposure. They do know that significant direct exposure over a long period of time makes it nearly certain. Many people have had some limited exposure without getting the disease. There are some factors like smoking that seem to hasten the onset of the disease. Hopefully your friends weren't exposed that much over too long a time. In your friend's situation and since they are so concerned I would recommend testing to see if they have had asbestos exposure. It's possible that there's nothing to worry about.

I prefer no texture on the ceiling. We're mid-reno right now. Tore out the plaster ceiling because we were running so much lighting that it made sense. Our plaster has a very random figure-8-ish texture. Very random. I know because I spent a ton of time when we first moved in patching small areas that needed attention. But, I digress. We have 8 foot ceilings and we are keeping the ceiling untextured. The rest of the walls (now a mixture of original plaster walls and some drywall) are going to have texture. We are having discussions with our guy right now trying to get him to get the texture right...did I mention that we have a random figure-8? Anyway, do you have texture on the rest of the walls? If you do and you're trying to match it, it might be difficult to do so. You don't want to go with a high-gloss paint for the ceiling - you'll see every variation of the ceiling. We opted for a satin finish for the ceiling...it's still got a bit of sheen, but not really glossy...I've found satin easy to clean (unlike a flat or even in some cases, an eggshell) if I wind up with a tomato sauce pop up on the ceiling. We're doing cabinets to the ceiling and we're hoping that gives a illusion of higher ceilings. We're thinking of doing a glass tile that has long thin strips, and if we run it vertical instead of horizontal, it will also help with the illusion of higher ceilings. Another thing that I think helps, is keeping simpler lines. I think that the more ornate things are (fancy countertop edges, complex cabinet door styles, etc) from the floor to eye level, the more your eye gets drawn to them and gets stuck from traveling upward.