Startups are hard. Too many startups are failing. Failure sucks. But entrepreneurs are persistent. That is a good thing. You only have to get it right once and rest will be an amazing journey. In the mean time, some startup ideas frequently fail. Most entrepreneurs who attempt them fail. Just a few entrepreneurs are able to pull them off. Established businesses on this list are doing great, the problem is how to reinvent these markets. Plenty of good ideas have not taken off as execution of the idea has been poor. These are some of the commonly attempted ideas that have been tried many times, and fail frequently.

1. RSS readers, or more generally, sites focused primarily on presenting and formatting news stories gleaned from 3rd party sources. Hundreds if not thousands of entrepreneurs have tried this idea. There is still a huge market for making sense of the hundreds of thousands of news stories everyday. So far, so good for Flipboard, Feedly, Zite, NewsWhip and the reinvention of Digg.

2. Craigslist killers are failing – but not sites that attack individual categories on Craigslist. While Craigslist offers a unique way to find goods and services online, there are several setbacks to the online classifieds platform: Scams run rampant, spam ads are frequent and the minimalist design lacks user-friendly appeal. Hoobly and Oodle are probably some of the biggest rival of Craigslist so far.

3. Reinventing the business card. For years, entrepreneurs seem to have thrown the kitchen sink (and more) at this problem, to no avail.  CardMunch, was a free app for converting business cards into digital address book contacts until. It was on to something, until LinkedIn acquired it and killed it. People just won’t give up their business cards that easily. But digital cards could be improved. Online business card ordering services like Moo are doing great printing and shipping business cards. There’s got to be a new way to use business cards.

4. You can’t kill email. Emails are here to stay but can be done better. Spamming is still a big problem. Sorting emails are still being figured out by new startups. Mailbox is doing great so far at making emails simpler. Remember the thousands of people who subscribed to be notified before Mailbox even launched. People still expect a lot more from their email services. Dropbox has acquired Mailbox. It doesn’t look like they will shut it down. That’s a good thing.

5.  Startups that dependent on communities tend to decline after initial success. Once communities reach a certain size they become difficult to manage. In some cases abuse is rampant or quality of content declines. Quora has successfully reinvented Yahoo Answers. Reddit is still strong. Quora is now stronger than ever. But there still room for niche Q and A sites.

6. Groupon type business models were tried dozens of times and have persistently failed, until Groupon. And now Groupon is slowly declining. Groupon’s “third-party” revenue, which measures its daily deal business, peaked and now appears to be in decline. People have begun ignoring those group discount emails. Even LivingSocial is struggling.

Not that people don’t like deals anymore but those emails could be too much to deal with, especially if you are not ready to make a purchase yet. If you are busy with work and keep getting Groupon deals, you will be frustrated and will unsubscribe. You want to get deals when you want it not when you are working and not even thinking about shopping. How then, do you determine when people need deals?

7. There are just too many dating apps out there. It is crowded and its scary but singles won’t stop looking for dates. The market will still be huge. Tinder is now the big thing out there. Some entrepreneurs are even applying the same swipe idea to other niches like job search. There are big players in the dating game but Tinder has been able to make a huge impression with a simple swipe idea. Tinder matches are not chatting as expected. It could peak and decline at some point. But so far so good for Tinder. The strategy works.

8. Any search company that’s not Google. The fact of the matter is Google, and to a much lesser extent Bing, own the search market. Yet, startups still spring up hoping to disrupt the incumbents. Cuil flopped. Wolfram Alpha is almost irrelevant. Powerset, which was a semantic search engine was bailed out by Microsoft. DuckDuckGo is the tiny closest search alternative to Google. Amid growing privacy concerns and a deal with Apple, DuckDuckGo has the potential to become a major player in search. It emphasizes protecting searchers’ privacy and avoiding the “filter bubble” of personalized search results.

9. Music startups can’t get enough paying customers. Music is still hot but it’s difficult to pull off because there are too many middlemen. If you don’t believe it, ask Spotify. They pay huge sums as royalties. Artists and producers deserve better if you solely depend on them to make a business. There are few successful web music ventures. Certainly no successful startups. iTunes is a success. Lala was barely working when Apple bought it. eMusic is not a smash hit. Even Amazon’s digital music business is tiny. Spotify is so far winning.