You can't just give out binaries without source, but you can choose not to release anything. The thing is, as usage models shift to include a lot of what the FSF very reasonably relabels SaaSS (Service as a Software Substitute), you can release nothing but provide the functionality over the network and reasonably expect people to use it that way. Since you haven't distributed the software itself to anyone, the GPL doesn't put you out of compliance for not showing them your code or letting them distribute it further.
This is the situation the Affero GPL (AGPL) was intended to address—it requires (or tries to require) that source code also be accessible to anyone who is given access to the software over a network. (Imprecisely speaking, that is; do check the license text if you want the specifics.)