That said, with the rising popularity of e-books (which I think will comprise 50% of the market by 2015), my theories and reasoning regarding self-publishing will change somewhat.
First, my words of caution re: unscrupulous self-publishing companies (read: vanity publishers) don't necessarily apply to the world of e-books, since nothing really stops you from just typing up a novel, converting it to the appropriate format, getting an ISBN, and uploading Ye Olde Lyfe's Worke all by yourself to any of the major e-book stores popping up on this swiftly tilting planet of ours. Easier yet, you could just convert the file to a .pdf and sell it through your personal website.
Second, since everyone in the industry is still getting their e-legs, they tend to scrutinize sales of electronic books a lot less severely than those of physical books. This means that if sales of your self-published e-book don't exactly blow up, it probably won't really hurt you (whereas a poor track record with a self-published physical book could definitely harm your prospects). This will probably change as e-book sales become the norm. (Trust me, while they may be the norm for you, they're not the norm for the industry.)
Third, self-publishing electronically is not (unlike physical self-publishing) a colossal waste of your time and money, since it can be done relatively quickly and cheaply (or even for free). The margin can also be very high, so you won't need to sell a huge number of copies to break even or turn a profit. In fact, if you don't count your writing time as time (and therefore money) spent, you can turn a profit after selling only one copy.
Now, the new caveats:
First, concerning uploading your book to Amazon/the iBookstore/&c or selling it yourself on your website: don't be shocked if nobody buys it. One of the major reasons authors develop into brand names is because a traditional publisher with good editorial, marketing, publicity, sales, and art teams has vetted the novel, gotten it into the public consciousness, possibly put it right at the front of the (e-)store, and slapped an eye-catching cover on it. You, as a début author whom know one knows and whose work hasn't been—in a word—legitimized by a traditional press, can't expect to see fantastic (or even decent) sales until and unless viral word-of-mouth sets in. (Hint: this is rare.)
Second, self-publishing electronically is easy—in fact, almost too easy. Don't be tempted to send your dear novel out into the e-ther early. Proofread, proofread, proofread. Have beta readers. Maybe even hire an editor. The good news: you're the boss! (The bad news: you're the boss.)
Finally, don't get your hopes up that electronically self-publishing will lead to your next book being picked up by a traditional house (complete with five- or six-figure advance), a movie deal, fame, glory, riches, or anything of the sort. Not that I expect you to—I just want to be sure we're all firmly grounded in reality.
Tomorrow: the (publishing) World of... Tomorrow!