Chinese internet companies are enormously overvalued.

WB monetized on online broadcasting. It worked pretty well in the past two years. However, competition in this industry is fierce. Attention of netizens comes easily and goes quickly. Retaining the public's attention span is very challenging.

Both Sina and Weibo are richly valued so they are very vulnerable to risks. 

I bought WB at $26 or so and sold when it was trading around $100. 

You've got to know the dynamics of an industry before you want to play the stocks. 

Good luck!