Sayonara Zetsubou-sensei comes to mind as a somewhat recent example (which shows my age even more than being in this sub, since the anime is almost old enough to vote at this point). It was very funny and even thought-provoking at times, but as the series went on it leaned further and further into ecchi/moe territory. They even broke the fourth wall and commented on it in the show at one point. What a shame.
Honestly: most series.
Sayonara Zetsubou-sensei comes to mind as a somewhat recent example (which shows my age even more than being in this sub, since the anime is almost old enough to vote at this point). It was very funny and even thought-provoking at times, but as the series went on it leaned further and further into ecchi/moe territory. They even broke the fourth wall and commented on it in the show at one point. What a shame.