Soft spot for [something]?

I always thought that "soft spot" is used for living things..

E.g.

1. soft spot for someone

2. soft spot for my pet dog

3. soft spot for the fishes in the pond

But I was wondering can it be used for non-living things as well.. for example:

1. He had a soft spot for numbers. <- does it make sense ?

2. He had a soft spot for counting. <- what about this

3. He had a soft spot for counting activities. <- better or worse?

Soft spot actually has two common meanings, and both of them can refer to inanimate objects.

The first meaning is the one to which you refer - essentially, a sentimental weakness for something. This is often used with living creatures simply because a kitten/baby/whatever more often pulls on our heartstrings than, say, a rock does. But you could, for instance, be a hardcore metal fan who has a soft spot for country music.

The other meaning of soft spot is an actual weakness (of the unemotional variety). This is more often than not used for inanimate objects - a soft spot in the economic recovery plan, a soft spot in the offensive line, etc.