Yes, there is nothing wrong with asking a voter for ID. There is no reason for a legitimate voter to refuse to provide ID to an election official before being permitted to vote. Carrying a valid ID is a requirement for tasks such as driving or drinking alcohol. It is appropriate to prove that is a person is who he or she says they are before allowing them to vote.
Voter fraud is extremely rare. It's virtually nonexistent. Even Fox News, an incredibly conservative "news" source, says it's rare (foxnews.Com/politics/2011/09/24/voter-id-laws-target-rarely-occurring-voter-fraud.Html). And it's usually conservatives who are pushing for voter ID laws. Also, there are numerous groups of people who are less likely to possess IDs. These groups include women, the elderly, young students, minorities, and the poor. And it's highly suspicious that it's usually conservatives who are pushing for these laws. Maybe the real reason is that they're trying to disenfranchise people who don't vote Republican.