While Romney is much richer than Obama, both men are incredibly wealthy. Romney has something like $230 million, while Obama got somewhere between $2.6 million and $9.9 million from his book sales. So why would anyone of modest means contribute anything to either campaign where neither fabulously rich guy at the center of the campaigns has kicked in a dime?
There are multiple precedents for candidates contributing money to their own campaigns. The first election I really remember, in 1992, featured H. Ross Perot spending tens of millions of his own money on half-hour infomercials. Michael Bloomberg and Meg Whitman each spent over $100 million running for New York mayor and California governor, respectively. Romney himself spent over $17 million on his 2008 campaign.
The Obama campaign had over 400,000 people donate an average of $50 last month. Romney similarly gets a decent haul from small donors, though he does get more from people giving $250+. However, these huge numbers of donors for each campaign doesn't include the candidates themselves. Instead, hundreds of thousands of middle class and poor voters are donating money so the rich candidates don't have to.
Self-funding one's campaign can often be taken as a sign of weakness. However, with the Obama campaign having just announced it has $115 million in cash on hand, now would be a great time for Obama to kick in a million or two. Until he does, he ain't gettin' nothin' from me.