Markus,
It depends on how you use the wildcard ssl certificate. Since ssl certificates also provide authentication information about the website, allowing random subdomains to be created on your domain can confuse users into believing your website endorses the random subdomains. For instance, if you allow users to create subdomains on your site www.your_good_name.com, they could in theory create a site https://stranger.your_good_name.com that leverages the wildcard certificate.
However, this is only if you 1) allow users to randomly create subdomains and 2) these subdomains can use your wildcard cert (you can install the cert on a seperate ip address where on ssl should be used and allow random users to create their subdomains on another ip address away from your ssl cert).
Otherwise, if sudomain creation is limited to a small number of trusted admins, then wildcard certificates are a great option from a cost and management standpoint.