I feel like an idiot for buying ZNGA at $3/share. Now, there is talk of having the company go from public back to private? What does this mean for me as a public shareholder?
I can see two possibilities.
Either a deal is struck that someone (the company itself, or a large owner) buys out the remaining shares. This is the scenario @mbhunter is talking about, so I won't go too deeply into it, but it simply means that you get money in your bank account for the shares in question the same as if you were to sell them for that price (in turn possibly triggering tax effects, etc.). I imagine that this is by far the most common approach.
The other possibility is that the stock is simply de-listed from a public stock exchange, and not re-listed elsewhere. In this case, you will still have the stock, and it will represent the same thing (a portion of the company), but you will lose out on most of the "market" part of "stock market".
That is, the shares will still represent a monetary value, you will have the same right to a portion of the company's profits as you do now, etc., but you will not have the benefit of the market setting a price per share so current valuation will be harder. Should you wish to buy or sell stock, you will have to find someone yourself who is interested in striking a deal with you at a price point that you feel comfortable with.