Here's how desperate some investors are to get into hot tech companies like Pinterest

There's a new investment trend in Silicon Valley that shows how overheated the investment market has become for hot startups. The Wall Street Journal reports today that venture capital firms like FirstMark Capital and Andreessen Horowitz are raising special "impromptu" funds from a few select investors, specifically to invest in late rounds in fast-growing companies with high valuations like Pinterest. Sometimes, these funds are coming together in days.  For instance, FirstMark reportedly wante...