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(An example of a case where a specific number might have meaning: a site that teaches about something, or that appeals to students. "Widgets 101" or "Widgets 900" would have instant meaning to your audience.)
Otherwise, not only is it hard to remember, but it emphasizes that your site is just one of many unmemorable sites that offers similar information, products, or services.
Your URL is the first thing many people see of your site. Don't start out sending the wrong message.
So I wonder, should I get an available 3 word domain, or just go after my target domain name and add a number at the end?
There's an axiom that may also apply to this situation/question:
And while this may, or may not, be "True" ...
(as draggar pointed out, he has a .org that ranks better than the .com ... he also said one's first instinct is to type in the .com)
... I think that example101.com only jumps the question of "Gee... I wonder what the real example.com has?"
Long 'round way of suggesting that a domain that includes your key word (widget), with one or two other descriptive (key) words in the .com domain name may be the better way to go.
If your content is good and accorate, you have the right keywords in the right place, the TLD is irrelevant to search engines.
It's sickening to see the .coms parked and people asking 5-6 figures for them. Heck, I've seen .com's go over $500-$1000 in drop-auctions (pennies compared to some, I know) while the exact domain, but a .net, .org, and .info, get ignored (and I've scarfed up a few at a registration fee).