First, there's plenty of blame to go around. Neither candidate is innocent.
Second, the amount of money Obama got from Fannie/Freddie employees is greater than the amount that McCain got... but as a proportion of their total dollars raised the difference isn't particularly huge, nor does it represent more than a drop in the bucket to the grand total raised. It's hard to get too upset over that in real life (as opposed to hyperpartisanland).
Third, while Obama got more money from Fannie/Freddie employees than did McCain, McCain got more money than did Obama from lobbying groups promoting Fannie/Freddie. This difference, both in proportion and actual dollars, was greater than the Obama/McCain gap from Fannie/Freddie employees. The total amount McCain got from these lobbyists was also proportionally more of McCain's total fundraising amount than the employees' contributions to Obama.
Now, if I were an honest man, I'd say that taking money from lobbying groups supporting Fannie/Freddie is worse than taking $20 contributions from Fannie/Freddie secretaries.
I have no problem with people knocking Obama for his legitimate Fannie/Freddie connections nor McCain for his de-regulatory bent; they're both true. But the intellectual honesty behind knocking Obama for taking more money from Fannie/Freddie employees is suspect at best.