I don't know that I'd say their the worst .. Pretty much all game companies these days do incredibly sleazy things including Valve. Valve's refusal to fix issues on their end with GFWL titles and Windows 8 users is both sleazy and annoying. (Several months after the launch of Windows 8, Valve continues to package Win8 incompatible versions of GFWL with GFWL titles on the platform despite all other merchants that offer downloaded GFWL titles fixing that issue months ago.)
That said I do think that EA is pretty horrible for pressuring BioWare to release DA2 before they were ready, and for all the issues/drama with SimCity. Also most of their really popular titles are crap while their really good and less popular titles get the axe. Their DRM is slightly less sleazy than UbiSoft's and they're very very slightly less greedy than Activision.
An internet poll you say? Of course someone like EA are going to get voted. Majority of gamers spend their lives on the internet (not meant in a bad way, exaggerated on purpose).
Now, I'm not defending EA, they are a pretty shitty company but, the fact people consider them worse than banks or companies causing oil spills speaks volumes about the voters. They are so upset about something like SimCity that they don't seem seem to give a fuck about their economy. Talk about priorities.
That EA were voted the "worst" company in the US means not a thing to me since I know for a fact that it's simply not true. (As said earlier, I think EA are a shitty company, try not rage at me please.)