Unfortunately, the degree.distribution() function of the igraph library returns the intensities of the distribution:

> g <- graph.ring(5)
> plot(g) 
> summary(g)
IGRAPH U--- 10 10 -- Ring graph
attr: name (g/c), mutual (g/x), circular (g/x)

So instead of having the number of elements, the density/intensities value is returned:

> degree.distribution(g)
[1] 0 0 1

You can easily verify this in the source code of the function:

> degree.distribution
function (graph, cumulative = FALSE, ...) 
{
    if (!is.igraph(graph)) {
        stop("Not a graph object")
    }
    cs <- degree(graph, ...)
    hi <- hist(cs, -1:max(cs), plot = FALSE)$intensities
    if (!cumulative) {
        res <- hi
    }
    else {
        res <- rev(cumsum(rev(hi)))
    }
    res
}

This caused me some minor issues, but the solution was easy. I simply created a new version of the function that is using $count instead of $intensities (BTW $intensities will be deprecated in R 3.0).

count.degree.distribution <- function (graph, cumulative = FALSE, ...) 
{
    if (!is.igraph(graph)) {
        stop("Not a graph object")
    }
    cs <- degree(graph, ...)
    hi <- hist(cs, -1:max(cs), plot = FALSE)$count
    if (!cumulative) {
        res <- hi
    }
    else {
        res <- rev(cumsum(rev(hi)))
    }
    res
}

Using it is identical to the original version:

> count.degree.distribution(g)
[1] 0 0 10