There've been larger single investments than that made, and of course pirate managed to borrow a shit-ton of BTC with essentially no business plan (I'm pretty sure he owes some individual lenders more than that).  

For the most part, though, people don't just throw money at ideas - those seeking funds, whether as debt or equity - need to be contributing and risking something of their own in the venture and have already done the research necessary to convince others of its viability.

Pretty much everyone on this board has access to at least two venture capitalists, but most ventures around here aren't the type of projects for which venture capital is most suitable (plus people around here hate sharing equity).  And most of the more pedestrian ventures people are looking to fund (there are very few truly novel ideas around here) aren't going to return enough to be attractive to the sub-prime lenders on this board.

There are definitely only a handful of projects/people I'd recommend to serious lenders/investors (and believe me, a lot of behind the scenes discussion goes on when those people are considering lending to people or investing in projects).  These threads are more suitable for people who only want to borrow a small amount of money/BTC for personal use or for those hoping to attract crowd funding.  They're not really the place to attract a couple of big lenders/investors for a project.

None of which means that the loans/investments made here are smart ones, only that loans and investments can be attracted here if you're pitching the right product.  That's not unique to this forum.  Got to any forum which is largely about getting maximum returns for minimal effort and you'll find similar dynamics.