One of Yahoo’s strongest properties will soon lose its head of product. Late yesterday, Matthew Rothenberg announced that he’s leaving Flickr after working at the organization for about five years.

To head off speculation, this move doesn’t necessarily relate to Yahoo’s decline or any planned changes at Flickr. Rothenberg wrote in a blog post, “Against all odds (and in the oddest of places), I have met someone who having a future with is more important to me than any job could ever be. Leaving Flickr behind will allow me to focus more passionately on investing in a future with her.”

Also, Rothenberg feels Flickr remains in capable hands. He later added, “I need to pass on the torch to the next generation of Flickreenos, all of whom have a clear mission, sense of purpose, and the drive and talent to get it done. I know that they are up for the task.”

Still, this does represent a blow for Yahoo and Flickr. Rothenberg noted that he was either employee number 12 or 13 at Flickr, and he’s helped the organization in a number of important ways (including establishing partnerships with Apple, Microsoft, Nokia, and RIM).

It’s hardly a secret that Yahoo’s been losing all sorts of key employees in recent weeks and months, either.

Anyway, Markus Spiering, a (former) senior product manager at Flickr, will replace Rothenberg on at least a temporary basis.