Users on the Steam forums are reporting that Skyrim's Steam Workshop integration carries an unfortunate downside. Apparently, you can only use the Workshop to subscribe to a maximum of 50 mods at once.
Try to install to more than that, and the next time you boot up the game you'll be greeted with the error message "Failed to enumerate subscribed files!". In other words, Skyrim can't count to 51. Whoops.
While 50 mods is hardly a miniscule limit — and honestly, you're likely to encouter some serious conflicts if you're running that many mods simultaneously — it's a bit strange that there's any limit to the number of mods you can install through the workshop, given that mods you download and install yourself don't appear to count towards that total.
We're betting this isn't an intentional limitation on Bethesda's part, and they'll likely patch it out before too much longer. In the meantime, we're forced to answer the toughest question mankind has ever known: Is our pet sabrecat more or less important than cooking clam chowder?