Working on revamping a plugin of mine when I noticed that
wp_count_terms() is not reflecting the same number as a call to
count( get_terms() ) with the same $args passed. I'm pretty sure this is a bug in WordPress and I'll submit a trac ticket in a little bit.
I wanted to get a solid working solution, so I ended up just making one call to
get_terms() and then using
count() on the array to get the count. My question is: "How many terms can be returned without slowing everything down". It's possible that there could be scaling issues here where there are a lot of terms in a taxonomy, but how many is TOO many? 1,000? 10,000? Just looking for a ballpark here.