Ann: Vocus announces granting of non-exclusive due diligence, page-26

Technically yes - but they will also quickly lose credibility as a financial sponsor / investor if they act as 'tyre kickers' or 'stalking horses' too often.

Also remember these people's time is expensive and they themselves are using other institutions' money not just to invest, but to cover their own overheads. If they spend it on loose bids and then have nothing to show at the end of the fund's life, they will probably find their next capital raising goes pretty poorly.