I suspect an author of a paper I'm reading was listed improperly - what to do? I was reading a paper. And the list of authors looks suspicious. Three of the authors are at some random place I haven't heard of and the fourth author is a well-known professor at a top university. The paper itself is not very good.

I suspect the well-known author may have been listed to improve the paper's chances of acceptance. (Most reviews in my field are only single blind.)
Of course, it is possible that nothing is wrong - I can't be sure.

Is there anything I can or should do?
Can? Yes - the comments already give you some hints: Look at the prof's website, try asking him a question about the paper.

Should? Probably not. If there is really something going on, then it would the business of the professor, not yours. If you proceed as above and ask him something, and there is really something fishy, he can decide by himself if something needs to be done.