you install a package with yum install, say pdftk, it will pull in a lot of dependencies:

Installed:  pdftk.x86_64 0:1.44-10.fc18Dependency Installed:  bouncycastle.noarch 0:1.46-6.fc18       itext-core.noarch 0:2.1.7-14.fc18       libgcj.x86_64 0:4.7.2-8.fc18            bouncycastle-mail.noarch 0:1.46-6.fc18  java-1.5.0-gcj.x86_64 0:1.5.0.0-40.fc18  sinjdoc.x86_64 0:0.5-13.fc18  bouncycastle-tsp.noarch 0:1.46-5.fc18  java_cup.noarch 1:0.11a-10.fc18  itext.x86_64 0:2.1.7-14.fc18     javamail.noarch 0:1.4.3-12.fc18Complete!

yum remove pdftk will remove only that package and not all the dependencies.

But you can look at all the 'transactions' (install, remove etc.):

$ sudo yum history list pdftkID     | Command line             | Date and time    | Action(s)      | Altered-------------------------------------------------------------------------------      88 | install pdftk            | 2012-12-14 13:35 | Install        |   11

And then you can undo that transaction:

$ sudo yum history undo 88Undoing transaction 88, from Fri Dec 14 13:35:34 2012    Dep-Install bouncycastle-1.46-6.fc18.noarch       @fedora    Dep-Install bouncycastle-mail-1.46-6.fc18.noarch  @fedora    Dep-Install bouncycastle-tsp-1.46-5.fc18.noarch   @fedora    Dep-Install itext-2.1.7-14.fc18.x86_64            @fedora    Dep-Install itext-core-2.1.7-14.fc18.noarch       @fedora    Dep-Install java-1.5.0-gcj-1.5.0.0-40.fc18.x86_64 @fedora    Dep-Install java_cup-1:0.11a-10.fc18.noarch       @fedora    Dep-Install javamail-1.4.3-12.fc18.noarch         @fedora    Dep-Install libgcj-4.7.2-8.fc18.x86_64            @fedora    Install     pdftk-1.44-10.fc18.x86_64             @fedora    Dep-Install sinjdoc-0.5-13.fc18.x86_64            @fedora    ...    Complete!