The S&P500 has roughly 11 sectors to it. Each one with its own ETF options. Each one of those sectors is also broken down by industry.
So in Facebook's case, you could get an ETF for the 10 sectors besides "Communication Services". Communication Services has less than 30 stocks. You could get an ETF for specific industries within Communication Services or just pick some of those stocks you like the most to add to your portfolio. Facebook's industry has only 4 other stocks I believe - Google (2), Twitter & TripAdvisor.
Of course the main downside to managing your own portfolio is re-balancing it.
But this is something I've considered from time to time when I feel very bearish on a certain company or industry that I feel my automated portfolio is overweight on.
EDIT: for those downvoting, please point to a retirement vehicle that does support shorting