-ová is the most common way to feminize last names in Czech and Slovak. For example, and the Czech tennis player Barbora Strýcová has a father named Jindrich Stryc. Her last name is the feminized form of her father's.

Likewise, in Russian you see "ova" whenever the woman's father or husband's last name ends in "ov," which is very common ending for Russian names. In this case, only the "a" has been added. Maria Sharapova has a father named Yuri Sharapov. Thus "ova" last names are not quite as common in Russian as in Czech or Slovak (almost all women's names in Czech and Slovak end in "ova"), but are still fairly common (and of course there's lots more Russians than there are Czechs or Slovaks).

You are noticing a lot of "-ova" endings for last names because you are watching lots of women's tennis. Russian, Czech, and Slovak males will not have last names that end in "ova" (NOTE HOWEVER: adding "ova" to the end is one way to make possessives out of male names in Czech and Slovak, and so you will see "ova" at the end of male names in this context--and this is where accent marks would help, because -ova is the possessive, whereas -ová is the feminized name). Of the top 100 female players whose names end in -ova, all are Russian, Slovak, or Czech. I point this out because this is not a standard ending for most Slavic cultures but, as far as I know, for these three only.

If someone comes around and has a more interesting answer that explains the history behind this convention, I will happily yield to them, but I believe this answers your question. And P.S. -- Most of those Czechs would prefer if you referred to them as "Central" Europeans. The Cold War is long over ;-).

I can slightly expand on what has been already said about the "-ová" suffix in Czech (and Slovak) in terms of linguistics. It helps facilitate what we call declension or more broadly inflection. That is, changes in the form of a word according to its use, such as different numbers or various grammatical cases.

To provide an example, in English you would say "give a gift to Michelle Obama", whereas in Czech you would say "dej dárek Michelle Obamové". The "Obamové" form is the dative case of the name, a form used when the noun or name is the recipient of something. Note there is no preposition "to" in the Czech equivalent, as by the declension of the word it already incorporates that particular meaning.

Male names are actually subject to the same treatment of declension. Thus Barack Obama can find his name written or spoken as "Obamy", "Obamovi", "Obamu", "Obamo" or "Obamou" in Czech under various circumstances. The sentence "give something to Obama" would be "dej něco Obamovi" if the president, not his wife, was to receive the gift instead.

Additionally, the use of the "-ová" suffix also conveys the information of the Obama in question being Michelle Obama and not Barack Obama, in case her first name would not be spelled out as above. This is where a difference between the male and female names lies, as only female names are affixed with "-ová" in the nominative case – the one you would use for the subject of a sentence – while male names stay the same.

There is some debate whether using the suffix is somehow disrespectful towards the female bearers of the name or if it is simply conforming to Czech linguistic norms, however, without it (or, more specifically, its effects on cases other than the nominative), a large part of the information conveyed by the word form would be lost.