Yes, theoretically you can flip the shares you agreed to buy and make a profit, but you're banking on the market behaving in some very precise and potentially unlikely ways. In practice it's very tricky for you to successfully navigate paying arbitrarily more for a stock than it's currently listed for, and selling it back again for enough to cover the difference. Yes, the price could drop to $28, but it could just as easily drop to $27.73 (or further) and now you're hurting, before even taking into account the potentially hefty commissions involved.
Another way to think about it is to recognize that an option transaction is a bet; the buyer is betting a small amount of money that a stock will move in the direction they expect, the seller is betting a large amount of money that the same stock will not. One of you has to lose. And unless you've some reason to be solidly confident in your predictive powers the loser, long term, is quite likely to be you.
Now that said, it is possible (particularly when selling puts) to create win-win scenarios for yourself, where you're betting one direction, but you'd be perfectly happy with the alternative(s).
Here's an example. Suppose, unrelated to the option chain, you've come to the conclusion that you'd be happy paying $28 for BBY. It's currently (June 2011) at ~$31, so you can't buy it on the open market for a price you'd be happy with. But you could sell a $28 put, promising to buy it at that price should someone want to sell it (presumably, because the price is now below $28).
Either the put expires worthless and you pocket a few bucks and you're basically no worse off because the stock is still overpriced by your estimates, or the option is executed, and you receive 100 shares of BBY at a price you previously decided you were willing to pay. Even if the list price is now lower, long term you expect the stock to be worth more than $28. Conceptually, this makes selling a put very similar to being paid to place a limit order to buy the stock itself.
Of course, you could be wrong in your estimate (too low, and you now have a position that might not become profitable; too high, and you never get in and instead just watch the stock gain in value), but that is not unique to options - if you're bad at estimating value (which is not to be confused with predicting price movement) you're doomed just about whatever you do.