When calling taxonomy_get_term_by_name(), the resulting term will be cached again and again on database, even though it is already in the cache table.
The broader issue is that entityCacheLoad(), when called with $conditions instead of $ids (e.g. in this case, $conditions = array(vid=xx and name=xx)), will not find the cached entry (since indexed via the indexKey), and will cache the results every time.
So each time an entity is loaded via $conditions, a cache_set will be done. Not helping performance, especially if your cache tables are still in database.
I know $conditions are apparently deprecated, but some core functions still use that, e.g. taxonomy_get_term_by_name.
A patch is incoming.