In this edition of The Motley Fool's "Ask a Fool" series, Motley Fool One analyst Jason Moser takes a question from a Fool reader, who asks:

I am a 29-year-old investor that has started a brokerage account aside from my 401(k) earlier this year. So far I have bought solely S&P index funds, but I am intrigued looking at some bond ETFs such as the Vanguard Long Term Bond ETF (BLV) and similar funds. The ratings are bad though, and the consensus seems to say this is a bad long-term investment. Should I feel comfortable buying low when people are bearish, or am I better off looking for safer buys?