According to minoxidil.com only rogaine users of the 5% minoxidil strength or better usually go through a shedding period, with 2% it is much less likely. The shedding is a sign that it is working and that newer stronger hairs will likely form in the future.
You have to stick with the product for atleast 4-6 months.
I only recently started finasteride 1mg and minoxidil 2%. I am adding minoxidil 15% soon though. I think I am experiencing very minor shedding with the 2% that I apply sometimes 3x a day.
The shedding period lasts 100 days. It doesn't always happen, especially not to a big extent. But I do believe the vast majority regrow the most of the hairs that fell out. It just speeds up the hair cycling from anagen to telogen to grow new, better hairs.
I don't have experience in this myself but I have read a ton about it. You can read a lot about shedding here: http://minoxidil.com/subpages/journa.../shedding.html