<s>
Breakup	B-Application
Notifier	I-Application
was	O
a	O
web	B-Application
application	I-Application
written	O
by	O
product	O
developer	O
and	O
programmer	O
Dan	O
Loewenherz	O
that	O
enabled	O
its	O
registered	O
users	O
to	O
track	O
the	O
relationship	O
status	O
of	O
their	O
Facebook	B-Application
friends	O
.	O
</s>
<s>
An	O
email	O
notification	O
was	O
sent	O
to	O
the	O
user	O
when	O
one	O
of	O
their	O
Facebook	B-Application
friends	O
changed	O
their	O
relationship	O
status	O
.	O
</s>
<s>
The	O
app	O
was	O
one	O
of	O
the	O
most	O
viral	O
Facebook	B-Application
app	O
's	O
at	O
the	O
time	O
of	O
its	O
release	O
.	O
</s>
<s>
Breakup	B-Application
Notifier	I-Application
gathered	O
100,000	O
users	O
in	O
less	O
than	O
24	O
hours	O
of	O
its	O
launch	O
and	O
reached	O
a	O
user	O
base	O
of	O
more	O
than	O
3,000,000	O
in	O
February	O
2011	O
.	O
</s>
<s>
Facebook	B-Application
then	O
blocked	O
the	O
app	O
.	O
</s>
<s>
Breakup	B-Application
Notifier	I-Application
was	O
later	O
unblocked	O
by	O
Facebook	B-Application
and	O
monetized	O
.	O
</s>
