There are hundreds of thousands of them. Really. According to the newest statistics published by the Ministry of Interior, there are 370 878 unique surnames in use in the Czech Republic. Not all of them are of Czech origin, many of them were brought to Bohemia, Moravia and Silesia in last few decades as people from other countries were moving in (yes, also these surnames are covered by those statistics).
Ministry of Interior publishes the surnames and names statistics every year. These statistics are available on its website, http://www.mvcr.cz/clanek/cetnost-jmen-a-prijmeni-722752.aspx?q=Y2hudW09MQ%3D%3D. There are xls and csv tables which are available for download. Those tables are not too well-arranged, but a group of statistics fans created a website which provides much better overview.
The website was already mentioned on this blog, but I think it's worth mentioning it again. The statistic tables were transformed into maps. These maps show you where the families with the chosen surname are living today. How it works?
There are tens of so called "authorized municipalities" which are responsible for larger area. The surname statistics are published for these authorized municipalities, so it's possible to divide the country into smaller pieces and show where the people with one surname are living. You won't get exact village, but you get at least an idea where to search for relatives, ancestors etc.
This can be, of course, used in case of less common surnames - there are thousands of Novák's, Dvořák's or Novotný's in the Czech Republic, but if your family has, for example, surname Machník (greetings to Stephen in Canada :o)), you'll clearly see what are the possibilities of the family origins. Let's see it in practice.
You have to type the surname you are searching for into the search area (in red circle).
After typing the surname, press Enter or click on Vyhledat (Search) button.
You'll get a map where the density of your surname is shown - the darker the color, the more often is the surname in that area (there are more people with this surname compared to the total number of inhabitants of that "authorized area"). There is a list of the "authorized municipalities" on the left where you see number of people having the surname in the area and density (Každý x-tý) of the surname. Machník surname is present 12 times in Strakonice area and every 7643rd man has this surname.
Příjmení: Machník, počet výskytů 57 v celé ČR. = Surname Machník, 57 occurences in whole Czech Republic.
When you move the mouse pointer above the area, it will show you its name and number of people having the chosen surname.
It's easy to use so don't hesitate to try it!