What about checking the exit status of the wget command?
I suppose that it should be different than 0, when wget is not able to download the complete file.
wget is actually downloading a "Thank you for downloading Skype" page (you can view the downloaded file in a Web Browser). You will need to find a direct download link, or download the file manually (assuming there's no way to wget can work around this, which I'm not aware of).
It is more complicated.
If I put the full address in my browser, I get 2 pop-up, One with the thanks screen, One with the open/save app ( open with ark in my case ).
If I click on the save option, I do not download the full file, only a partial copy. In that case I can verify the size of the file.
This arise sometimes on some kind of internet site.
Note that the version delivered is not the same as the version requested. They redirect to the latest version, but you can hack the Location header's URL to fetch the originally requested version.
By the way, a little time with Firefox or Chrome developer tools is very useful when diagnosing these annoyances.