I started over a month ago, as I said, and I've actually expierenced LESS hair falling out than before. I have long, thick, curly and frizzy hair that I shed like a dog in summer everyday. While I've been on Alli, I barely lose half of what I was. Even when I lost all that, everyday, you couldn't tell. I contribute the slowing down of hair loss to my better diet, and indirectly Alli.
It IS perfectly natural to lose about 100-200 strands of hair a day from breakage and what have you, Alli or not. If you wear a lot of product or keep your hair up, you will appear to be losing more in the shower or something because that would prevent the hairs that naturally fall out from leaving your head, so you could have 2-3 days worth stuck.
Just keep in mind that some hair loss through your day is perfectly natural. If you don't take a mutlivitamin or you cut out a lot of stuff from your diet such as all good fats, protein, etc, this is also likely going to make your hair more fragile, and Alli strongly advices you not to do that, and to find a good balance. Alli tells you to take a MV, it's one of the first things on the box, so I am surprised when I see people say they aren't (usually not on these fourms, but others I go to). It's very important!
I think most people (perhaps not all, but most), that say they lose hair could of possibly been following the wrong sort of diet. You should meet your fat/cal intake Alli tells you to - or only go safely below that, and not to an extreme. You don't have to eat fat-free EVERYTHING. Having a light dinner? Put real dressing on your salad! Don't strive to keep it as low as possible, just strive to keep it at your limit. People that only want to eat 3-5g of fat per meal just aren't doing it right, and that is bad for your body.
All in all, I think theres no doubt Alli is indirectly responsible for these peoples hair loss. It's pretty hard to get it all right and balanced at the start. However, its the change in your diet, lack of MV and the fact that Alli will block out some nutriants that cause it - not the medication itself. If you notice significant hairloss, check your diet really good and make sure you're well balanced. Make sure your MV has everything Alli blocks.