What are examples of when seq_along works, but seq produces unintended results?

Question

What are good examples of when seq_along will work, but seq will produce unintended results?

From the documentation of ?seq we

Answer 1

If the input to seq is length 1 then the outputs between seq and seq_along will be different

x <- 5
for(i in seq(x)){
    print(x[i])
}
#[1] 5
#[1] NA
#[1] NA
#[1] NA
#[1] NA

for(i in seq_along(x)){
    print(x[i])
}
#[1] 5

We also see a difference if the input is a vector of Dates

x <- Sys.Date() + 1:5
seq(x)
#Error in seq.Date(x) : 'from' must be of length 1
seq_along(x)
#[1] 1 2 3 4 5