If you're not going to build a brand then .com is not really necessary, although its nice to have it on your domain.
Alternative when .com is not available.
You can use either .net or .org, or even .info and .biz if your really want the Exact Match Domain (EMD).
Hyphenated domains can rank as well as non-hyphenated domains. This is also a great alternative if the non-hyphenated .com domain is not available.