Could it be the variety? Some kinds of strawberries are cultivated to be bigger, and I know that wild strawberries usually stay small (like M&Ms). Or maybe the plant didn't get enough water? My raspberries tend to be bigger when they get more water.

I am having similar problem. Our bed is two years old. It seems to be running amok....many many berrites, but many are small, maybe marble sized. And not much flavor. Plants are Junebearind and Everbearing. Should go through and cull a bazillion small ones every now and then? Maybe they need a shot of Miraclegrow or something?
Wife says fertilize. I say discard four out of five and things will improve. What do you think?

they love mulch and MANURE! I feed mine a load of poo every other spring. This is the first year I've actually had a gorgeous little batch (my bed isn't large) of strawberries. They are also very prone to heat stress and need to be watered frequently or you get hard, sour little berries. So keep them mulched to keep them cool and moister (then treat for slugs) and enrich the soil heavily. That's the way my dad and I have been doing it for years and every time we mess it up we have lame crops...

-Marie

Water them more and you'll get bigger berries. We had a long stretch there of no rain, so if you weren't watering, then the plants were having to struggle to get enough moisture to make decent berries.

Mulch and manure or fertilizer are probably good ideas, but too late now to have much effect this year.

You might also have alpine strawberries... they are very small, esp. compared to newer cultivars, but they are supposed to be very flavorful.

Julie - if you got these from me they are the alpine types and won't get very big. Water does make them bigger, but they won't be any larger than your small fingernail!

Very tasty tho

Lynn