Based on the aggregated intelligence of 170,000-plus investors participating in Motley Fool CAPS, the Fool's free investing community, biotech company MannKind (Nasdaq: MNKD) has received a distressing two-star ranking.

With that in mind, let's take a closer look at MannKind's business and see what CAPS investors are saying about the stock right now.

MannKind facts

Headquarters (Founded) Valencia, Calif. (1991)
Market Cap $1.23 billion
Industry Biotechnology
Trailing-12-Month Revenue $93,000
Management Founder/CEO Alfred Mann (since 2003)
CFO Matthew Pfeffer
Return on Capital (Average Past 3 Years) (54.1%)
Three-Month Return 45.4%
Competitors sanofi-aventis (NYSE: SNY)
Eli Lilly (NYSE: LLY)
Novo Nordisk (NYSE: NVO)

Sources: Capital IQ (a division of Standard & Poor's) and Motley Fool CAPS.

On CAPS, 17% of the 668 members who have rated MannKind believe the stock will underperform the S&P 500 going forward. These bears include JuanPeter and All-Star zzlangerhans, who is ranked in the top 1% of our community.

This month, JuanPeter didn't exactly express high hopes for MannKind's inhaled insulin product, Afrezza: "[A] 4 week delay won't prevent Afrezza from being rejected by the FDA. ... [P]rior FDA decisions on inhalable drugs citing concerns on long term safety won't make this one an easy play. ... Make your bets!"

At negative 54.1%, MannKind's three-year average return on capital is substantially lower than rival Sanofi's 7.9%, Lilly's 21.2%, and Novo's 26.3%. Of course, for MannKind, it's all about Afrezza going forward, but with both Pfizer (NYSE: PFE) and Novo having given up on inhaled insulin in recent years, many Fools are skeptical about MannKind's long-term potential.

CAPS All-Star zzlangerhans elaborates:

At this price level, I see more downside in the short-term regardless of the PDUFA outcome. I think another technical CRL is the most likely verdict, but I'm far from sure that's what will happen.

The main long-term issue, as always, is whether inhaled insulin represents a genuine improvement over injected insulin. The FDA has certainly questioned this in the past, and I've yet to meet a diabetic who didn't take his insulin because of fear of needles.

What do you think about MannKind, or any other stock for that matter? If you want to retire rich, you need to protect your portfolio from any undue risk. Staying away from dangerous stocks is crucial to securing your financial future, and on Motley Fool CAPS, thousands of investors are working every day to flag them. CAPS is 100% free, so get started!