Deactivating the second account from your PS3 will make all of the content from that account inaccessible. However, if you reactivate the account, the content will be accessible again.
Answer from this source:
When a PS3 is activated under a given PSN account, it can run the software downloaded (purchased) from the PlayStation store under that
PSN account. The activation is automatic the first time you log in
with a given PSN account, meaning whatever you download from then on
will work fine.
Deactivating a PS3 (or a PSP) basically makes content downloaded under a given PSN account unreadable on that system. You can safely
try this yourself. Deactivate your system - try launching any already
downloaded game (wont work) - re-activate your system - content will
now work fine as before.
This is mostly useful when you want to share stuff you downloaded (purchased) with other people. To do so you have to let them log in as
you from their PS3s. So you basically have to give them your log in
data (email + password). Once they log in as you, their PS3s are
automatically activated (hence, by accessing the "Download List"
section on the PS store, they can re-download for free and run on
their systems all the stuff you purchased). When a grand total of 5
PS3s are activated under the same PSN account (this includes your own
system), no more PS3s can be activated, therefore you cannot share
your PSN account with more that 4 other people at a time.
If, say, you want to share your PSN account with a new friend but have all those extra 4 activations already in place on other PS3s, you
have to de-activate one of these so that your new friend can activate
his system under your PSN account.
Also note that deleting a profile via the XMB from a PS3 doesn't automatically deactivate it under the PSN account associated to that
profile. It has to be "manually" deactivated from the account
management page in order to free one of those 5 activations. So if a
friend of yours is using your PSN account and decides to dispose of
his PS3 system, tell him to do the deactivation thing (log in as you >
Account Management > Activate System > PlayStation 3 (this system) >
Deactivate system), otherwise you'll lose one of your possible
activations. Simply deleting the profile associated with your PSN
account or formatting the HDD is not enough.
This seems to be a generally accepted answer across multiple forums. This has been quoted several times with positive responses.