Well, it's not really essential to find a bottom, just to find an inefficient market, i.e., with all the public information out there, a security is simply priced wrong. This was the case 18 months ago. But some people argue that pockets of inefficient markets ALWAYS exist.
Right now i think many US stocks are inefficiently priced by selling too high, not many too low. Companies like Yahoo constantly paying their employees with options grants, for example - hiding the true costs of their business. Yahoo made .03 last quarter after considering options; is this a good return for a $30.00 investment?
I ask myself, if i had $400 million would i consider using all this money to buy a business like Travelzoo (TZOO's market cap), with $3M in net tangible assets but which seems to have earned $3M in a year (that's without considering the real cost of stock options). Of course i wouldn't - then why would i buy the shares at this price? Unfortunately there are hundreds of companies like this, so the bull case for me is hard to see.
Once upon a time, companies actually generated enough cash from their operations to pay shareholders 5-10% dividends and had plenty left over to grow their businesses. That was before corporate officers started the stealing game.